Gynecologic Oncology

Transcription

1 Gynecologic Oncology 126 (2012) Contents lists available at SciVerse ScienceDirect Gynecologic Oncology journal homepage: Review Clear cell carcinoma of the ovary: A review of the literature Marcela G. del Carmen a,, Michael Birrer b, John O. Schorge a a Division of Gynecologic Oncology, Vincent Obstetrics and Gynecology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA b Division of Medical Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA article info abstract Article history: Received 6 March 2012 Accepted 16 April 2012 Available online 21 April 2012 Keywords: Clear cell Ovarian Cancer Surgery Objective. Different histologic types of epithelial ovarian cancer may represent different diseases with unique clinical and molecular characteristics. Clear cell carcinoma (CCC) of the ovary has been reported as having a worse prognosis than high grade serous epithelial ovarian cancer (EOC). This article critically reviews the literature pertinent to the pathology, pathogenesis, diagnosis, management, and outcome of patients with ovarian CCC. Methods. MEDLINE was searched for all research articles published in English between January 01, 1977 and January 30, 2012 which reported on patients diagnosed with ovarian CCC. Given the rarity of this tumor, studies were not limited by design or number of reported patients. Results. Ovarian CCC tumors represent 5 25% of ovarian cancers. Its histologic diagnosis can be challenging, resulting often times in misclassification of these tumors. Ovarian CCC tends to present at earlier stages and has been associated with endometriosis, ARID1A and PIK3CA mutations. When compared to stagematched controls, patients with early-stage ovarian CCCs may have a better prognosis than patients with high-grade serous tumors. For those with advanced stage disease, high-grade serous histology confers a better prognosis than ovarian CCC. Patients with Stage IC IV have a relatively poor prognosis and efforts should center in discovery of more effective treatment strategies. Conclusions. Ovarian CCC is a biologically distinct entity, different from high-grade serous EOC. Future studies should explore the role of targeted therapies in the management of ovarian CCC Elsevier Inc. All rights reserved. Contents Introduction Methods Epidemiology Pathology Pathogenesis Clinical presentation Prognosis Treatment Surgery Chemotherapy Radiation therapy Future directions Conclusions Conflict of interest statement References Corresponding author at: Division of Gynecologic Oncology, Vincent Obstetrics and Gynecology, Massachusetts General Hospital, 55 Fruit Street, Yawkey 9E, Boston, MA 02114, USA. Fax: address: mdelcarmen@partners.org (M.G. del Carmen) /$ see front matter 2012 Elsevier Inc. All rights reserved. doi: /j.ygyno

2 482 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) Introduction Epithelial ovarian cancer is the most lethal gynecologic malignancy. Effective screening strategies are lacking and most women are diagnosed with advanced stage disease. An estimated 22,280 new cases of ovarian cancer will be diagnosed in the United States in 2012, with close to 15,500 deaths [1]. Epithelial ovarian cancer (EOC) accounts for 90 95% of all cases, while sex-cord stromal tumors and malignant germ cell tumors remain rare. Various randomized, controlled clinical trials have been carried out and their results largely guide the management of most women with EOC. These trials are not discussed in the present review. Methods This article reviews the English language literature for studies on clear cell ovarian cancer. A 35-year period MEDLINE (PubMed) search of English literature published between January 01, 1977 and January 30, 2012 was performed. All publications with the keyword ovary were combined and then searched for the keyword clear cell. Additional publications were identified via systematic review of all reference lists within publications retrieved from the MEDLINE search. Given the rarity of this tumor, and the concomitant lack of data in the form of large trials, all peer reviewed original report publications with an appropriate number of subjects were considered and included. Epidemiology Clear cell carcinoma (CCC) of the ovary accounts for 5 25% of all EOC, depending on the geographic location [2]. In North America and Europe, CCC is the second most common histologic sub-type of EOC, with an estimated prevalence of 1 12% [2 6]. In Japan, the prevalence of CCC is 15 25%, with a reported increase from 2002 to 2007, from 19% to 24.5%, respectively [7 10]. Among Asian women living in the United States, CCC was diagnosed twice as frequently (11.1%), when compared to white women (4.8%) [11]. Pathology In 1973, the World Health Organization (WHO) defined ovarian CCCs as tumors with clear cells growing in solid, tubular or glandular patterns, and hobnail cells lining cysts and tubules [12]. In 2003, the WHO updated the definition of CCC to describe a neoplasm composed of clear cells, growing in a solid, tubular or papillary pattern, with hobnail cells lining tubules and cysts (Figs. 1 and 2) [13]. Given the rarity of these tumors, correct pathologic diagnosis can be challenging. Studies of CCCs reporting high rates of advanced stage disease at presentation, and high response rates to platinum-based chemotherapy, features more commonly associated with high-grade serous EOC, suggest that ovarian CCCs are often misclassified as serous EOC [14,15]. Han et al. reported on a series of tumors of mixed serous and clear cell histology, with similar stage, immunophenotypes and mitotic activity of those of pure serous histology, concluding that they likely represent pure serous EOC with clear cell changes [16]. In the study by Gilks et al., 23% of 575 cases of low-stage CCC cases were identified as such at review and were not reported as CCC at the time of original diagnosis [17]. In a different study, frozen section diagnosis was accurate for CCC only 41% of the time [18]. Given their distinctive biological and clinical features, the correct classification of ovarian CCCs is of critical importance. Several authors have described specific morphologic and immunohistochemical features that can be utilized to improve accuracy of pathologic classification. Immunohistochemical markers, including hepatocyte nuclear factor 1-beta (HNF1B), Wilms tumor 1 (WT1), estrogen receptor (ER), progesterone receptor (PR) and tumor protein 53 (p53) can be used. Ovarian CCCs stain positive for HNF1B and negative for WT1, ER, PR and p53. High-grade serous EOC have the opposite staining pattern [19 21]. Table 1 summarizes the different features characterizing ovarian CCC and high-grade serous EOC. Mixed carcinomas with high-grade serous and clear cell features have been problematic in terms of diagnostic reproducibility. These mixed tumors are indistinguishable from high-grade serous EOC with respect to clinical, immunohistochemical and histopathologic features, such as mitotic index. Thus, some have suggested the term high-grade serous cancer with clear cell features, proposing that they represent a variant of high-grade serous EOC and are not related to CCCs. [16]. Mixed endometrioid-clear cell carcinomas are rare, accounting for approximately 1.3% of EOCs, but representing the most common mixed ovarian carcinoma [5]. This mixed histology is not surprising given that both endometrioid and clear cell EOC are associated with endometriosis and share reported mutations in the AT-rich interactive domain 1A [SWI-like] gene (ARID1A) and phosphatidylinositol 3-kinase (PI3K) pathway. Pathogenesis The molecular and genomic biology of CCC, although not entirely elusive, remains less well-understood than that of high-grade serous EOC. The most significant molecular features associated with CCC are summarized in Table 1. CCCs, unlike high-grade serous EOCs, are generally p53 wild-type, with a lower frequency of BRCA (breast cancer) Fig. 1. Clear cell carcinoma of the ovary, depicting the characteristic tubulo-cystic histologic pattern.

3 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) Fig. 2. Serous carcinoma of the ovary with clear cell features, showing the more pleomorphic papillary pattern characteristic of serous ovarian cancer. 1 and 2 germline mutations [22 28]. CCC tumors have low levels of chromosomal instability and low proliferation rates, with high frequency of phosphoinositide 3-kinase catalytic alpha (PIK3CA mutations) [10,22,26,29]. The frequency of PIK3CA mutations in these tumors has been estimated to be 40%, with some investigators suggesting that the PI3K AKT mtor HIF (phosphoinositide 3-kinase, v-akt murine thymoma viral oncogene homolog, mammarian target of rapamycin, and hypoxia induced factor) pathway may be a target with therapeutic potential [29 31]. CCCs have been associated with common regions of DNA gain, including 17q23 25, which correlates with increased expression of the 17q23 protein-phosphatase 1D gene (PPM1D), negative regulator of p38/mapk (mitogen-activated protein kinase), and in turn, p53- mediated transcription and apoptosis, and negative regulator of checkpoint kinase CHK1 and G2/M cell cycle arrest [32 36]. PPMD1 overexpression has been associated to poor outcome [33]. In approximately 7% of CCCs, the scaffolding subunit of protein phosphatase 2 (PP2A) and protein phosphatase 2 regulatory subunit A (PPP2R1A) has been shown to be mutated, clustered around conserved repeated HEAT motifs [37]. Gene expression profile similarities of endometrial, ovarian and renal clear cell carcinomas have been documented, raising the possibility of similar ontogeny and possible common targeted therapeutic strategies [38,39]. For example, insulin-like growth factor 2 mrnabinding protein 3 (IGF2BP3) is an independent prognostic marker in ovarian and renal clear cell carcinomas [40,41]. Hypoxia inducible factor 1, alpha (HIF1a), the VHL target, is overexpressed in ovarian CCCs when compared to other EOC histologies [42 44]. Birrer and Anglesio have reported that CCC expression profile signature appears to revolve around hypoxia, cytokine and oxidative stress pathways [43 45]. In the study by Stany et al., major activated pathways in clear cells involving angiogenesis, hypoxic cell growth, and glucose metabolism not seen in other EOC histologies were described [43]. Pathways appear to involve interleukin (IL)- and signal transducer and activator of transcription 3 (STAT3) converging on HNF1B, HIF1A, and endothelial PAS domain-containing protein 1 is (EPAS1) [43 46]. 1. In the study by Stany et al., the authors conclude that the activated pathways suggest a mechanism for the poorer prognosis of patients with CCC when compared to serous ones. Clear cells may have the capacity to survive in an environment with limited nutrients and oxygen [43]. When compared to serous cell lines, clear cells were less likely to be affected by hypoxia (1% O 2 ) and glucose deprivation. Disruption of the glycolytic or angiogenic pathways may sensitize the cells to these conditions affording them a survival advantage. These pathways may be therapeutic targets. Sunitinib has generally been described to target platelet-derived Table 1 Characteristics of ovarian clear cell and high-grade serous carcinomas. Clear cell High-grade serous Higher incidence among Asian women Higher incidence among European women Younger age at presentation Older age at presentation Low stage at presentation Advanced stage at presentation (Stage I/II in 57 81% of cases) (Stage III/IV in approximately 80% of cases) Associated with endometriosis Associated with serous tubal intra-epithelial carcinoma Low frequency of BRCA 1/2 mutations Higher proportion of BRCA 1/2 mutations Higher frequency of thromboembolic events Lower frequency of thromboembolic events Higher resistance to first-line platinum and taxane-based chemotherapy Higher response rates to first-line platinum and taxane-based chemotherapy Stain positive for HNF1B (85 93%) Stain negative for HNF1B Stain negative for WT1, ER, PR and p53 Stain positive for WT1, ER, PR and p53 (65 96%) p53 wild-type (85%) p53 mutant (93%) Higher frequency of ARID1A mutations (46%) ARID1A mutations not detectable Higher frequency of PIK3CA mutations (33%) Low frequency of PIK3CA mutations BRCA 1/2 = breast cancer 1, breast cancer 2. HNF1B = hepatocyte nuclear factor 1-beta. WT1 = Wilms tumor 1. ER = estrogen receptor. PR = progesterone receptor. ARID1A = AT-rich interactive domain 1A [SWI-like] gene. PIK3CA = phosphoinositide 3 kinase catalytic alpha. Table modified with permission from Reference # 38.

4 484 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) growth factor receptor, beta polypeptide. (PDGFRB), KIT and vascular endothelial growth factor receptor (VEGFR). These receptors are not overexpressed in CCCs, Sunitinib seems to target tyrosine kinases and growth factor receptors [47]. Sunitinib may act primarily on the microvasculature [48]. Yamaguchi et al. have reported on a gene signature, specific to clear cell cancer, lending support to sunitinib's wider spectrum of targets being expressed in the epithelium [18]. In their study, these investigators carried out gene expression microarray analysis using 38 ovarian cancer cell lines and were able to identify genes commonly expressed in both ovarian CCC cell lines and clinical samples, comprising an ovarian CCC gene signature [18]. The signature they described is characterized by expression of markers such as HNF-1beta and versican (VCAN), and other genes reflecting oxidative stress [18]. Sunitinib's reported effect on growth and viability of CCCs, distinct from serous EOCs, highlights sunitinib's potential use as a targeted agent in the treatment of ovarian CCCs [43]. Combination therapy of sunitinib and RNAi shows synergistic activity in ovarian CCCs, providing the rationale for targeted therapy in patients with ovarian CCC [43]. Possibilities would include agents targeting angiogenesis (antibodies, for example) and drugs inhibiting tumor metabolism (mtor inhibitors) [43]. Despite the many similarities between ovarian and renal CCC, they represent different diseases. While renal clear cell cancer shows somatic and germline mutations in the VHL gene, these have not been shown in ovarian CCC tumors [38]. ARID1A, a tumor suppressor, appears to be mutated in close to 50% of CCC cases [37,43,44,49]. BRG-associated factor 250A (BAF250A), an ARID1A gene product, is a component of SWI/SNF (SWItch/Sucrose NonFermentable) chromatin-remodeling complex and interacts with several cytokine and hypoxia related transcription factors, such as HIF1 and STAT3 [43,44,50,51]. Cytokine and hypoxia signaling and transcriptional control via the SWI/SNF complex appear to be critical molecular events in the pathogenesis of CCCs [38]. Table 2 summarizes the most important molecular events that characterize ovarian CCC. Table 2 Critical molecular events in ovarian clear cell carcinoma. Gene/ reference number Pathway Definition p53/22,25,26 Wild-type DNA damage/apoptosis sensor PTEN/42 PI3K AKT mtor HIF Loss of protein expression (approximately 1/3 of cases) PPP2R1A/37 PP2A complex, G2/M checkpoint Clustered mutations (approximately 7% of cases) PPM1D/ 32,33 Negative regulation of p38/ MAPK, and G2/M Over-expression and amplification (approximately 10% of cases) PIK3CA/37 PI3K AKT mtor HIF Activating mutation (approximately 40% of cases) MTOR/31 PI3K AKT mtor HIF Higher levels of activated phosphormtor HNF1B/45 Several, enrichment of transcription factor genes Clear cell histology-specific biomarker ARID1A/ 37,49 SWI/SNF chromatin remodeling Loss of function/truncating mutations (approximately 50% of cases) P53 = tumor protein 53. PTEN = phosphatase and tensin homolog. PPP2R1A = protein phosphatase 2 regulatory subunit A. PPM1D = protein phosphatase, Mg 2+ /Mn 2+ dependent, 1D. PIK3CA = phosphoinositide 3-kinase catalytic alpha. mtor = mammalian target of rapamycin. HNF1B = hepatocyte nuclear factor 1-beta. ARID1A = AT-rich interactive domain 1A [SWI-like] gene. PI3K AKT mtor HIF = phosphoinositide 3-kinase, v-akt murine thymoma viral oncogene homolog, mammarian target of rapamycin, and hypoxia induced factor. PP2A = protein phosphatase 2 regulatory subunit A. MAPK = mitogen-activated protein kinase. SWI-SNF = SWItch/Sucrose NonFermentable. Table modified with permission from Reference # 38. Clinical presentation Women with ovarian CCC present at a younger age than women with serous EOC (mean age 55 vs 64, respectively) [11]. Ovarian CCC is also more commonly associated with thromboembolic disease, some authors reporting a thromboembolic event in as many as 40% of patients with ovarian CCC, which is double the rate in matched non- CCC controls with EOC [2,52,53]. Olsen et al. documented an increased body-mass index (BMI) associated with ovarian CCC [54]. The study did not control for race [54]. Other studies have shown inconsistent results on the relationship of BMI and CCC [54 57]. Patients with ovarian CCC usually present with a pelvic mass [38,58]. The size of the mass ranges from 3 to 20 cm, with most tumors detected pre operatively either by clinical exam or imaging [59]. In an in vitro model of EOC, cells from clear cell tumors remain attach to mesothelial cells, without invading for 18 h, compared to serous tumors, which invade rapidly into the mesothelium [60]. This behavior may in part explain the propensity of CCC tumors have to remain localized until they form a pelvic mass [58]. Ovarian CCC tumors tend to present at earlier stages. In large institutional series, comparing early (I/II) vs late (III/IV) stage EOC, 47 81% of CCC tumors were diagnosed at early stages [7,11,59,61,63 65]. For example, in the study by Rauh-Hain et al., inclusive of 121 patients with ovarian CCC, and one of the largest in the literature, Stages I and II were reported in 48.4% of patients at initial diagnosis [62]. The underlying explanation for clear cell cancers presenting with earlier stage disease remains elusive. Possible explanations proposed include its association to endometriosis, and its low proliferation rate [38]. Much of the variation reported in frequency of CCC among different trials may be due to these notable differences in stage distribution [38]. Ovarian CCCs comprise only 1 5% of patients with advanced stage EOC in chemotherapy trials, largely due to their overall low incidence and propensity for low-stage disease at the time of initial diagnosis [4]. Ovarian CCC has been associated with endometriosis, with endometriosis-associated ovarian cancer tending to occur in younger women, 5 6 years earlier than high-grade serous EOC [62,66 70]. In the study by Rauh-Hain et al., endometriosis was identified in 45% of patients with ovarian CCC [62]. Some authors have suggested that atypical endometriosis may be a precursor lesion [71,72]. In a large population-based study from Japan, endometriosis resulted in a nine-fold increased risk of developing ovarian cancer [73]. The breakthrough finding of ARID1A mutations in almost half of ovarian CCCs has renewed the interest in elucidating molecular pathways for these tumors that may explain their unique biology [38]. Prognosis The management strategy for advanced stage EOC centers around efforts to achieve maximal cytoreduction and deliver platinum plus paclitaxel-based chemotherapy. The specific effects of this treatment paradigm remain unproven for ovarian CCC given that only a small percentage (2%) of patients in trials investigating this regimen have had a diagnosis of CCC [74]. The discussion of prognostic and therapeutic results in the management of ovarian CCC is limited given the rarity of this histology, the retrospective nature of most available series, and the possible pathologic misclassification in making the correct histologic diagnosis. The available data from retrospective, institutional series reporting on outcomes among patients with ovarian CCC have several limitations. The use of recently described morphological criteria and immunohistochemical marker panels, discussed earlier, has lead to a dramatic increase in inter-observer reproducibility of ovarian CCC [75,76]. However, this technology was not available at the time of publication of numerous retrospective studies reporting on clinical outcomes among women with ovarian CCC. Furthermore, many of

5 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) these studies lack central pathology review. Many of these investigators use serous EOC as the comparison group in their series, and do not distinguish between ovarian low-grade and high-grade serous carcinomas, which based on recent evidence, may represent different entities and not part of a continuum of serous tumors [22,76 80]. Combining these two different tumors can confound analysis. The role of maximal cytoreductive effort in the management of serous and clear cell EOC has an important prognostic value [81 83]. However, many of these studies do not document information on cytoreduction or control for it in their analysis of the data, which may be a potential confounder. Although many investigators have studied and compared the prognosis of patients with ovarian CCC to those with serous EOC, conflicting results have been reported. Studies dating back to the 1970s noted no difference in outcome between these two groups [84,85]. Kennedy et al. reported similar survival for women with early stage ovarian CCC compared to other EOC histologies but worse survival for patients with Stage III/IV ovarian CCC when compared to patients with advanced stage non clear cell EOC [66]. More recent studies have reported a poor prognosis for women with advanced stage ovarian CCC [7,62,65,66,86,87]. A study conducted by the Gynecologic Oncology Group (GOG), exploring the role of cisplatin plus cyclophosphamide with or without doxorubicin in the treatment of Stage III ovarian CCC, noted a poor outcome to platinum-based chemotherapy among these patients [2]. Response rate to chemotherapy in patients with CCC ranges from 11 to 45%, with documented high rates of disease progression ranging from 52 to 81% [7,62,88]. Survival rates for women with advanced stage ovarian CCC are also reported to be lower than that of patients with serous EOC. In the study by Pectasides et al., median survival for patients with ovarian CCC was 25.1 months (95% CI, months, range 2.4 to months) and 49.1 months (95% CI, months, range months) for patients with serous EOC [88]. This difference was not statistically significant (p=0.141) [88]. Goff et al. reported a shorter median survival for patients with ovarian CCC when compared to survival in patients with serous histology [2]. Another study noted that CCC histology was associated with the worst prognosis in patients with Stage III and IV EOC of all types, except for those with tumors of mucinous histology [86]. In the series by Sugiyama et al., median survival for patients with Stage III ovarian CCC was 12.7 months, statistically significant and lower than the reported median survival of 26.8 months reported for patients with serous EOC [7]. Low survival rates in ovarian CCC may in part reflect these tumors' lack of sensitivity to platinum-based chemotherapy. Our study of 121 patients with ovarian CCC is in line with other studies in correlating low response rates to chemotherapy to poor survival [7,62,65,66,86,87]. The study by Gorai et al. supports this rationale. In this study, ovarian CCC cells exhibited resistance to cisplatin [89]. However, given the retrospective nature of our study and the others cited, firm conclusions on this relationship cannot be reached. The mechanism responsible for this possible platinum resistance has not been clearly delineated but may involve a decrease in the accumulation of platinum and an increase in detoxification of the drug within the cell, as well as an increase in DNA repair [90 92]. Chemotherapy resistance may also be related to the low proliferation rate associated with ovarian CCC [93,94]. Presently, there are no antineoplastic agents definitely active and effective in the treatment of ovarian CCC and mechanism of chemotherapy resistance remains elusive. The future may rest on use of targeted therapies in the treatment of ovarian CCC. Treatment Surgery Given the rarity of ovarian CCC, the role that staging and cytoreductive surgery may play in its management has not been prospectively evaluated. Given that an estimated 49-56% of ovarian CCCs present as Stage I disease, the role of staging surgery warrants exploration. In a retrospective study of 205 patients with ovarian CCC, staging was not associated with improved survival [95]. The authors did not conduct a subgroup analysis in order to identify a low-risk group. Greater than 80% of patients in the study received adjuvant chemotherapy [95]. In a study including several Japanese institutions, 199 patients with early stage ovarian CCC were evaluated, with 135 patients (68%) undergoing lymphadenectomy as part of the staging surgery [96]. Lymph node metastases were seen in 10 patients (7.4%) [96]. On univariate analysis, both lymph node status and cytology were associated with progression-free survival (PFS) [96]. Only positive cytology/ascites remained significant in affecting PFS on multivariate analysis [96]. The reported hazard ratio for positive lymph nodes was 3.7 (CI, ), vs 2.1 (CI, ) for positive cytology/ascites [96]. The p value for positive lymph nodes carried borderline significance (p=0.05) for PFS [96]. There were no factors in patients with early stage disease predicting overall survival on multivariate analysis [96]. Although the authors did not describe the details, over 90% of patients in the study received adjuvant chemotherapy, and 3 out of the 5 patients in the node positive group who developed recurrent disease were long-term survivors [96]. In our study, 41.8% of 121 patients with ovarian CCC underwent lymphadenectomy compared to 70.7% of patients with uterine CCC who had a lymph node dissection [62]. Patients with uterine CCC had a higher rate of metastases to lymph nodes, when compared to patients with ovarian CCC (14.6% vs 11.4%, respectively, p- value=0.03) [62]. Ninety percent of the patients with ovarian CCC vs 34.1% of those with uterine CCC received adjuvant chemotherapy [62]. Lymphadenectomy was not associated with survival on multivariate analysis for neither group. As shown by Takano et al., positive cytology has been reported as an adverse prognostic indicator in several other studies, with relapse rates as high as 35% in patients with Stage IC disease [7,61,66,81,96]. Historically, given the observed poor prognosis of patients with ovarian CCC, most have recommended adjuvant therapy, even for those with early stage disease [38]. The reported high frequency of capsule rupture may be an influencing factor in this recommendation. In the EORTC-ACTION trial, capsule rupture was noted in 44% of ovarian CCCs vs only 19% of serous EOCs, with 85 90% of cases of rupture in ovarian CCC due to intra operative rupture [97]. When compared to patients with early-stage serous EOC, patients with early stage ovarian CCC rarely had bilateral tumors (2% vs 10%) or obvious pelvic extension (3% vs 10%) [97]. Although recent studies suggest that prognosis for Stage I ovarian CCC is similar to prognosis of patients with Stage I serous EOC, results may be confounded by accuracy of pathologic diagnosis and treatment strategies [38]. Survival for ovarian CCC patients was 85.3% as compared to 86.4% for patients with serous EOC in the SEER database study [11].In a different study, 5-year survival for patients with Stage I ovarian CCC was 76% and 73% in patients with serous ovarian cancer [98]. In a recent study, with contemporary pathology review, reported 10-year survival for 35 patients with Stage IA/IB ovarian CCC was 87% as compared to 68% for those with same stage of disease, serous EOC [61]. In this same study, patients with adhesions from the pelvic mass to the pelvic sidewall that required sharp surgical dissection had their tumors upstaged to a FIGO Stage II lesion and had a worse outcome [99]. In the subset analysis of patients with CCC assigned to the observation arm of the EORTC-ACTION trial, 5-year disease-free survival (DFS) was similar to DFS of patients with serous EOC (71% vs 61%, respectively, p=0.2) [97,100]. In this trial, patients with CCC treated with chemotherapy had a 5-year DFS of 60%, statistically similar to the 71% noted in patients assigned to the observation arm [97,100]. Given the risk of lymph nodal metastases associated with ovarian CCCs that appear clinically confined to the ovary, as well as the possibility that the lack of survival benefit associating with lymphadenectomy is the result of confounding variables inherent to the retrospective

6 486 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) nature of most of the available trials, we recommend staging procedures to fulfill FIGO criteria for all patients surgically appropriate for staging surgery. In patients with surgically Staged IA ovarian CCC, consideration should be given to surgical therapy only, given the results discussed above. Future studies should try to identify patients with low-stage ovarian CCC who would benefit from adjuvant systemic therapy. In carefully selected and counseled patients, fertility-sparing surgery, usually followed by adjuvant chemotherapy, may be appropriate. This treatment strategy has been reported to be successful, albeit in series with small number of patients [99,101]. Surgical debulking is an important component of the treatment paradigm for women with advanced stage or metastatic disease. In our study, subset analysis of women with advanced stage ovarian CCC, optimal cytoreduction was associated with improved overall survival, after multivariate analysis [62]. Cytoreduction should be evaluated prospectively, given that CCC is less responsive to chemotherapy [4,70,102,103]. Chemotherapy Combination chemotherapy, with platinum plus paclitaxel has been adopted as the standard regimen for front line treatment of EOC [74,104,105]. Historically, women with ovarian CCC have been eligible for participation in first-line and other chemotherapy trials, including the ones establishing the role of carboplatin and paclitaxel in front line treatment. It has been difficult to evaluate the specific impact this regimen has had on the prognosis of women with ovarian CCC, given the confounding effects of low numbers of patients with this histology and disproportionate representation of low-stage CCC tumors in these trials [38, ]. In 2004, the Gynecologic Cancer Intergroup could not reach a consensus on the clinical implications of CCC histology [38]. In order to address the prognostic significance of CCC and other rare histologies of EOC, the Rare Ovarian Histologies Working Group was organized and sought assistance to address these questions from international intergroup databases created from completed randomized clinical trials [112]. In 2010, a meta-analysis including data from seven international Phase III platinum-based first-line trials, with over 8000 patients, was published [4]. The analysis included 221 (2.5%) of women with Stage III/IV CCC, who when compared to women with advanced stage serous EOC, were reported to have a less favorable outcome, with increased risk of death (HR=2.18; 95%CI ) and disease progression (HR=1.64; 95%CI ) [113]. For patients with CCC, median OS was 21.3 months (95% CI months) compared to a median OS of 40.8 months (95% CI months) for women with serous EOC [113]. No statistically notable differences were seen between studies with and without central pathology review [113]. This meta-analysis lends support to international collaborative efforts to accrue patients to histology-specific trials [38]. Some studies indicate that CCC may be resistant to standard carboplatin-paclitaxel based chemotherapy regimens. The reported response rate (RR) to first-line therapy with this regimen from retrospective series ranges between 22 and 56%, compared to RR of over 70% for patients with serous EOC [7,81,88, ]. Several other authors report similar response rates for patients with ovarian CCC when compared to those with serous EOC, although, as noted earlier, these studies may be confounded by historical classifications of serous tumors [102]. In our study of 121 patients with ovarian CCC, response rate to carboplatin paclitaxel-based first-line chemotherapy was 79%. In each case, the diagnosis of CCC was confirmed by a pathologist with expertise in gynecologic oncology [62]. At 6 months, following completion of chemotherapy, 24% of these patients developed recurrent disease [62]. When multivariate logistic regression was used to control for other factors independently associated with platinum resistance (age, residual disease, and spread of disease), only sub-optimal cytoreduction and spread of disease were associated with a significantly increased risk of platinum resistance [62]. Recio et al. showed that platinum-based chemotherapy did not improve 5-year overall survival when compared to OS in patients who were treated with non-platinum based regimens (36% vs 32%) [117]. Chemoresistance (progression of disease on chemotherapy) may, at least in part, explain the poor response ovarian CCC has to platinum-based regimens. As noted earlier, the mechanism underlying CCC's chemoresistance to platinum-based therapy is not well understood. Presently, there are no large-scale trials to inform on the antineoplastic agents that are definitively effective in treating ovarian CCC. In vitro chemosensitivity of 23 antineoplastic agents using four established cell lines has been investigated [118]. Irinotecan was noted to be active in ovarian CCC [118]. In a different study, the cytotoxicity of chemotherapeutic agents in four ovarian CCC and two serous cell lines was studied [119]. Paclitaxel was more efficacious in CCC than serous cell lines [119]. Intensification of cytotoxicity was seen in combinations of cisplatin plus paclitaxel and cisplatin plus cyclophosphamide or 5-FU, irrespective of histopathologic features, suggesting that individualized treatment strategies may improve outcomes in patients with ovarian cancer [119]. Ovarian CCC may have higher mrna levels of ERCC1 and XPB, key genes in the nucleotide excision repair pathway, which may be indicative of de novo drug resistance against DNA-damaging drugs [120]. Clinical studies specific to patients with ovarian CCC necessitate multi-group collaboration and significant institutional efforts to enroll patients, often recruiting 1 2 patients per institution per year. Despite these challenges, several studies specific to women with ovarian CCC have been executed. Combination doublets with cisplatin plus irinotecan and mitomycin-c with irinotecan have been reported to be effective [121,122]. In a Phase II study of combined irinotecan and mitomycin-c of 25 patients with cisplatin-refractory clear cell and mucinous EOC, an overall RR of 52% and a median survival time of 15.3 months were reported [122]. Tanaka et al. also evaluated combination irinotecan and mitomycin-c. Combination of a fixed dose of nedaplatin and rising dose of irinotecan in patients with advanced stage ovarian CCC resulted in a pathologic complete response [123,124]. In another Phase II study, the Japanese Gynecologic Oncology Group (JGOG) compared irinotecan hydrochloride plus cisplatin (CPT-C) to carboplatin and paclitaxel [125]. Both regimens were tolerated well, with a reported 70% of patients completing six cycles of chemotherapy. Progression-free survival between the two groups was similar [125]. In a subset analysis of patients with less than 2 cm of residual disease after surgical cytoreduction, PFS was longer in the CPT-C arm, although this difference did not reach statistical significance (p=0.2702) [125]. An international Phase III, lead by the JGOG, with an accrual target of 662 patients has completed enrollment. This trial is comparing carboplatin and paclitaxel to irinotecan and cisplatin in patients with Stage I IV ovarian CCCs. In the recurrent setting, response rates to subsequent chemotherapy are rather low. In a retrospective study, among 39 women whose tumor had not responded or only partially responded to first-line chemotherapy, there were no responses to second-line therapy [102]. In a Japanese study of 75 patients with CCC treated with at least two lines of systemic therapy, patients whose tumors recurred greater than 6 months after completion of first-line therapy had a RR of 8% compared to a RR of 6% in patients whose tumors progressed within 6 months of completing primary therapy [103]. Median OS for women with platinum sensitive disease was 16 months, compared to 7 months for those with platinum resistant disease (p=0.04) [103]. The authors conclude that recurrent or resistant CCC is extremely chemoresistant, with a need for exploration of novel targeted therapies. Table 3 summarizes chemotherapy studies in the treatment of ovarian CCC. Given the retrospective nature of the studies, as well as the time range reported, it is not possible to describe all chemotherapy regimens used. The studies described in the table include series reported before the formal institution of platinum and taxanebased chemotherapy regimens in the treatment of EOC.

7 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) Table 3 Summary of chemotherapy studies in the treatment of ovarian clear cell carcinoma (CCC). Reference number/ author Publication year Study type FIGO stage Number of patients with ovarian CCC Number of patients in comparison group Chemotherapy regimen a [66]/Kennedy 1989 Retrospective I IV non-occc Platinum and non-platinum based Median OS (months) Stages I II similar to CG Stages III IV worse than CG [86]/Omura 1991 Retrospective analysis of GOG 22 and 47 Suboptimal Stages III IV non -OCCC GOG 22 b GOG 47 c 6.7 months (OCCC) 16.4 (months) serous EOC [2]/Goff 1996 Retrospective Stage III serous EOC Platinum-based 12 months (OCCC) 22 months (CG) [117]/Recio 1996 Retrospective Stages III IV non OCCC Platinum and non-platinum based [63]/Kennedy 1999 Retrospective Stages I IV non-occc Platinum and non-platinum based Similar 5-year OS in OCCC, platinum vs non-platinum chemotherapy (36% vs 32%) Matched for stage and grade, similar OS in OCCC and CG [7]/Sugiyama 2000 Retrospective Stages I IV serous EOC Platinum-based 31.8 months (Stage I/II OCCC) 12.7 months (Stage III OCCC) 17.8 months (Stage IV OCCC) 42.3 months(stage I/II CG) 26.8 months (Stage III CG) 19.4 months (Stage IV CG) [115]/Ho 2004 Retrospective Stages III IV 31 9 mixed-type OCCC Platinum and paclitaxel-based [88]/ Pectasides [116]/ Utsunomiya 11 months (OCCC) 48+ months (CG) 2006 Retrospective Stages III IV serous EOC Platinum-based 25.1 months (OCCC) 49.1 months (CG) 2006 Retrospective Measurable primary and recurrent OCCC 28 None Platinum and paclitaxel-based [137]/Lee 2011 Meta-analysis Stages I IV ,648 non- OCCC Platinum and non-platinum based [62]/Rauh- Hain 2012 Retrospective Stages I IV uterine CCC Platinum-based chemotherapy OS = overall survival. OCCC = ovarian clear cell carcinoma. CG = comparison group. GOG = Gynecologic Oncology Group. EOC = epithelial ovarian cancer. HR = hazard ratio. a Chemotherapy is reported only for studies that explored discrete number of regimens. b Study compared melphalan vs melphalan+hexamethylmelamine vs cyclophosphamide+doxorubicin. c Study compared cyclophosphamide +doxorubicin vs cyclophosphamide +doxorubicin +cisplatin. Combination regimen may have greater efficacy than platinum-only regimen OCCC had higher HR of death than non- OCCC 106 months (OCCC) 41 months (uterine CCC) Radiation therapy Radiation therapy can be an effective treatment modality for some patients with EOC. However, the use of radiation therapy in the management of EOC has fallen out of favor since effective chemotherapy can be given with lower toxicity profiles. In patients with intermediate-risk tumors (high-risk Stage I, Stage II and Stage III lesions with no residual or minimal residual disease limited to the pelvis), the use of whole abdominopelvic radiation therapy (WAR) results in improved OS when compared to pelvic radiation therapy. This finding is likely the result of lower rates of upper abdominal recurrence in patients treated with WAR [38,126]. There is data to show that radiation therapy may improve survival when used following completion of chemotherapy [38,127,128]. In the study by Gelblum et al., close to 70% of patients with chemoresistant EOC who underwent radiation therapy following systemic treatment had resolution of their symptoms [129]. In a study of 16 patients with ovarian CCC, 14 of whom had Stage IC/ II, 5-year OS in the radiated group was 83% compared to 33% for the historical controls treated with platinum-based chemotherapy [130]. In a retrospective study of 700 patients, 375 with endometrioid, clear cell or mucinous EOC, treated with platinum-based chemotherapy alone or combination platinum-based chemotherapy and WAR, an improved OS was seen in patients with endometrioid, clear cell or mucinous tumors treated with the combination strategy [131]. Specifically, 175 patients with ovarian CCC were included in the study. The authors reported a 40% reduction in cancer-specific deaths, corresponding to an improved 10-year survival rate (78% combination treatment vs 52% chemotherapy only) [131]. Based on these studies, it may be appropriate to consider the design and execution of a randomized trial of patients with Stage IC II ovarian CCCs, assessing combination chemotherapy and pelvic radiation is more effective than radiation alone, or whether pelvic radiation alone is superior to chemotherapy alone. Future directions Therapeutic innovations in the treatment of ovarian CCC tumors rely on translational basic science research informing the design of clinical trials investigating targeted therapies. Possible choices include agents that target angiogenesis (antibodies, tyrosine kinase inhibitors) and inhibit tumor metabolism (mtor inhibitors). Sunitinib malate, an oral agent, has been approved as standard treatment for CCC of the kidney and gastrointestinal stromal tumors [38,132,133]. It inhibits tumor proliferation and angiogenesis, targeting VEGFR,

8 488 M.G. del Carmen et al. / Gynecologic Oncology 126 (2012) PDGFR, KIT and other tyrosine kinases and growth factor receptors [38,134,135]. Dual inhibitors targeting PI3K, AKT in the mtor pathway are also promising. There is anecdotal evidence of sunitinib activity in ovarian CCC [47]. GOG 254, currently undergoing active accrual, is a Phase II trial of sunitinib in the treatment of persistent or recurrent ovarian CCC. Another possible target is the PI3K AKT mtor pathway. Phase I/II trial data exists for agents such as rapamycin, temsirolimus, everolimus and deferolimus. In a small series of patients, 3 out of 6 women with CCC had a response to temsirolimus [136]. An increasing understanding of the biology of CCC tumors will continue to facilitate the emergence of promising targeted therapies. Given the challenges intrinsic to the execution of a trial of rare tumors, institutions invested in contributing to innovation in the management of patients with ovarian CCC should consider trials done with the help of international collaboration, powered subset analysis done within larger EOC trials, and crossover trial designs, optimizing enrollment opportunities [38]. All future trials should consider expert pathologic review and tissue collection to facilitate correlative studies enhancing the translational component, with the ultimate goal of discovering novel therapies that may improve outcome for patients with ovarian CCC. Conclusions Ovarian CCC continues to be managed using the treatment paradigm that has been adopted for other EOCs. CCC represents a distinct clinical challenge with a unique and different biology when compared to high grade serous EOC. Given our present understanding of its unique biology, future investigations should focus on the identification of clinical, pathologic, and molecular features of select patients, such as those with Stage I disease, who may not necessitate adjuvant systemic therapy and may be cured with surgery alone [38]. Patients with ovarian CCC should undergo comprehensive surgical staging. Patients with Stages IC IV have a relatively poor prognosis and efforts should center in discovery of more effective treatment strategies [61]. All of these patients should be considered for participation in appropriate clinical trials. The role of adjuvant radiation therapy warrants further investigation in the management of patients with Stage IC/II disease. A trial needs to be undertaken to better define the role of this treatment modality. Intergroup collaboration is critical for the appropriate accrual and execution of trials evaluating the role of novel therapies that will specifically target the molecular pathways unique to ovarian carcinoma, with the goal of ultimately improving outcome for these patients. Conflict of interest statement None of the authors have any conflict of interests to report. References [1] Siegel R, Ward E, Brawley O, Jemal A. Cancer statistics, CA Cancer J Clin 2012;62: [2] Goff BA, Sainz de la Cuesta R, Muntz HG, Fleischhacker D, Ek M, Rice LW, et al. Clear cell carcinoma of the ovary: a distinct histologic type with poor prognosis and resistance to platinum-based chemotherapy in stage III disease. Gynecol Oncol 1996;60: [3] Piccard MJ, Bertelsen K, Jame K, Cassidy J, Mangioni C, Simonsen E, et al. Randomized intergroup trial of cisplatin paclitaxel versus cisplatin cyclophosphamide in women with advanced epithelial ovarian cancer: three-year results. J Natl Cancer Inst 2000;92: [4] Mackay HJ, Brady MF, Oza AM, Reuss A, Pujade-Lauraine E, Swart AM, et al. Prognostic relevance of uncommon ovarian histology in women with stage III/IV epithelial ovarian cancer. Int J Gynecol Cancer 2010;20: [5] Kobel M, Kalloger SE, Huntsman DG, Santos JL, Swenerton KD, Seidman JD, et al. Differences in tumor type in low-stage versus high-stage ovarian carcinomas. Int J Gynecol Pathol 2010;29: [6] Vasey PA, Jayson GC, Gordon A, Gabra H, Coleman R, Atkinson R, et al. Phase III randomized trial of docetaxel carboplatin versus paclitaxel carboplatin as first-line chemotherapy for ovarian carcinoma. J Natl Cancer Inst 2004;96: [7] Sugiyama T, Kamura T, Kigawa J, Terakawa N, Kikuchi Y, Kita T, et al. Clinical characteristics of clear cell carcinoma of the ovary: a distinct histologic type with poor prognosis and resistance to platinum-based chemotherapy. Cancer 2000;88: [8] Japanese gynecologic cancer committee. Annual report on Japanese gynecologic cancer committee. Acta Obstet Gynaecol Jpn 2002;54. [9] Japanese gynecologic cancer committee. Annual report on Japanese gynecologic cancer committee. Acta Obstet Gynaecol Jpn 2009;61. [10] Itamochi H, Kigawa J, Terakawa N. Mechanisms of chemoresistance and poor prognosis in ovarian clear cell carcinoma. Cancer Sci 2008;99: [11] Chan JK, Teoh D, Hu JM, Shin JY, Osann K, Kapp DS. Do clear cell ovarian carcinomas have poorer prognosis compared to other epithelial cell types? A study of 1411 clear cell ovarian cancers. Gynecol Oncol 2008;109: [12] Serov SF, Scully RE, Sobin LH. International histological classification of tumors, November 9. Histologic typing of ovarian tumors. Geneva: World Health Organization; p [13] Tavasolli FA, Devilee P. World Health Organization classification of tumors. Tumors of the breast and the female genital organs. Lyon: IARC Press, WHO; p [14] Nagai Y, Inamine M, Hirakawa M, et al. Postoperative whole abdominal radiotherapy in clear cell carcinoma of the ovary. Gynecol Oncol 2007;107: [15] Ohishi Y, Oda Y, Kuihari S, et al. Hobnail-like cells in serous borderline tumor do not represent concomittant incipient clear cell neoplasms. Hum Pathol 2009;40: [16] Han G, Gilks CH, Leung S, Ewaniwich CA, Irving J, Longacre TA, et al. Mixed ovarian epithelial carcinomas with clear cell and serous components are variants of high-grade serous carcinoma: an interobserver correlative and immunohistochemical study of 32 cases. Am J Surg Pathol 2008;32: [17] Gilks CB, Ionescu DN, Kalloger SE, Kobel M, Irving J, Clarke B, et al. Tumor cell type can be reproducibly diagnosed and is of independent prognostic significance in patients with maximally debulked ovarian carcinoma. Hum Pathol 2008;39: [18] Yamaguchi K, Mandai M, Oura T, Matsumura N, Hamanishi J, Baba T, et al. Identification of an ovarian clear cell carcinoma gene signature that reflects inherent disease biology and the carcinogenic process. Oncogene 2010;29: [19] Kobel M, Kalloger SE, Carrick J, Huntsman D, Asad H, Oliva E, et al. A limited panel of immunomarkers can reliably distinguish between clear cell and high-grade serous carcinoma. Am J Surg Pathol 2009;33: [20] DeLair D, Oliva E, Kobel M, Macias A, Gilks CB, Soslow RA. Morphologic spectrum of immunohistochemically characterized clear cell carcinoma of the ovary: a study of 155 cases. Am J Surg Pathol 2011;35: [21] Tsuchiya A, Sakamoto M, Yasuda J, et al. Expression profiling in ovarian clear cell carcinoma: identification of hepatocyte nuclear factor 1-beta as a molecular marker and a possible molecular target for therapy of ovarian clear cell carcinoma. Am J Pathol 2003;163: [22] Kobel M, Kalloger SE, Boyd N, McKinney S, Mehl E, Palmer C, et al. Ovarian carcinoma subtypes are different diseases: implications for biomarker studies. PLoS Med 2008;5:e232. [23] Salani R, Kurman RJ, Giuntoli R, Gardner G, Bristow R, Wang TL, et al. Assessment of TP53 mutation using purified tissue samples of ovarian serous carcinomas reveals higher mutation rate than previously reported and does not correlate with drug resistance. Int J Gynecol Cancer 2008;18: [24] Ahmed AA, Etemadmoghadam D, Temple J, Lynch AG, Riad M, Sharma R, et al. Driver mutations in TP53 are ubiquitous in high grade serous carcinoma of the ovary. J Pathol 2010;221: [25] Skirnisdottir I, Siedal T, Karlsson MG, Sorbe B. Clinical and biological characteristics of clear cell carcinomas of the ovary in FIGO stages I-II. Int J Oncol 2005;26: [26] Kuo KT, Mao TL, Jones S, Veras E, Ayhan A, Wang TL, et al. Frequent activating mutations of PIK3CA in ovarian clear cell carcinoma. Am J Pathol 2009;174: [27] Kobel M, Reuss A, Bois A, Kommoss S, Kommoss R, Gao D, et al. The biological and clinical value of p53 expression in pelvic high-grade serous carcinomas. J Pathol 2010;222: [28] Risch HA, McLaughin JR, Cole DE, Rosen B, Bradley L, Fan I, et al. Population BRCA1 and BRCA2 mutation frequencies and cancer penetrances: a kin-cohort study in Ontario, Canada. J Natl Cancer Inst 2006;98: [29] Campbell IG, Russsell SE, Choong DY, Montgomery KG, Ciavarella ML, Hooi CS, et al. Mutation of the PIK3CA gene in ovarian and breast cancer. Cancer Res 2004;64: [30] Kobayashi K, Kajiwara K, Kanayama S, Yamada Y, Furukawa N, Noguchi T, et al. Molecular pathogenesis of endometriosis-associated clear cell carcinoma of the ovary (review). Oncol Rep 2009;22: [31] Miyazawa M, Yasuda M, Fujita M, Kajiwara H, Hirabayashi K, Tekekoshi S, et al. Therapeutic strategy targeting the mtor HIF-1alpha VEGF pathway in ovarian clear cell adenocarcinoma. Pathol Int 2009;59: [32] Tan DS, Lambros MB, Rayter S, Matrajan R, Vatcheva R, Gao W, et al. PPM1D is a potential therapeutic target in ovarian clear cell carcinomas. Clin Cancer Res 2009;15: [33] Hirasawa A, Saito-Ohara F, Inoue J, Aoki D, Susumu N, Yokoyama T, et al. Association of 17q21 q24 gain in ovarian clear cell adenocarcinomas with poor prognosis and identification of PPM1D and APPBP2 as likely amplification targets. Clin Cancer Res 2003;9: [34] Lu X, Nannenga B, Donehower LA. PPM1D dephosphorylates Chk1 and p53 and abrogates cell cycle checkpoints. Genes Dev 2005;19: [35] Suehiro Y, Sakamoto M, Umayahara K, Iwabuchi H, Sakamoto H, Tanaka N, et al. Genetic aberrations detected by comparative genomic hybridization in ovarian clear cell adenocarcinomas. Oncology 2000;59:50 6.