Follicular lymphomas

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1 Critical Reviews in Oncology/Hematology 66 (2008) Contents Follicular lymphomas Umberto Vitolo a, Andrés J.M. Ferreri b,, Silvia Montoto c a Hematology Unit, Azienda Ospedaliera S. Giovanni Battista Molinette, Turin, Italy b Unit of Lymphoid Malignancies and Medical Oncology Unit, Department of Oncology, San Raffaele H Scientific Institute, Milan, Italy c Department of Medical Oncology, St. Bartholomew s Hospital, London, United Kingdom Accepted 31 January Definition, incidence and risk factors Pathology and biology Morphology Immunophenotype Genetic features Clinical presentation and natural history Staging Staging procedures Staging system Molecular analysis of minimal residual disease Prognostic factors Treatment Watch and wait policy Treatment of stages I II low-grade follicular lymphoma Treatment of stages I II with high tumor burden and/or high-risk follicular lymphoma Treatment of stages III IV follicular lymphoma Treatment of stages III IV high-risk follicular lymphoma Maintenance treatment of stages III IV follicular lymphoma Treatment of relapsed or refractory follicular lymphoma Treatment of high-grade transformed follicular lymphoma New drugs and combinations in follicular lymphoma References Biographies Abstract Follicular lymphomas constitute 30% of all non-hodgkin lymphomas. These lymphomas are characterized by at least partially follicular growth pattern, but diffuse areas may be present. The proportions of follicular or diffuse areas vary also from case to case, which seems to be associated with prognosis. Follicular lymphomas should not be divided into distinct subtypes, but rather shows a continuous gradation in the number of large cells. On the bases of this grading, three groups have been defined: grades 1 3. There is a consensus that grade 3 follicular lymphomas, namely grade 3b, should be discriminated from lower-grade cases. The cells of follicular lymphomas express surface immunoglobulin, more frequently IgM +/ IgD > IgG > IgA, B-cell-associated antigens, CD10+/ ; they are CD5, CD23 /+, CD43, and CD11c. Follicular lymphomas express bcl-2 proteins, which is useful in distinguishing reactive from neoplastic follicles. t(14;18) is present in 70 95% of follicular lymphomas, involving rearrangement of bcl-2 gene. Clinical behavior of follicular lymphomas is heterogeneous and differs according to the histologic grade and extension of disease. Moreover, the evaluation of these malignancies is conditioned by therapeutic decision, which is also determined by main prognostic factors. The International Prognostic Index for aggressive lymphomas is not optimal Corresponding author at: Medical Oncology Unit, Department of Oncology, San Raffaele H Scientific Institute, Via Olgettina 60, Milan, Italy. Tel.: ; fax: address: andres.ferreri@hsr.it (A.J.M. Ferreri) /$ see front matter 2008 Elsevier Ireland Ltd. All rights reserved. doi: /j.critrevonc

2 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) for follicular lymphomas. Conversely, the Italian Lymphoma Intergroup Index and, more recently, the Follicular Lymphoma International Prognostic Index (FLIPI), designed in pre-rituximab era, seem to correlate well with outcome. Several active therapeutic approaches from the wait and watch strategy to the allogeneic transplantation are available for management of patients with follicular lymphoma. Therapeutic decision is mostly conditioned by patient s characteristics, stage, histologic grade, tumor burden, and risk-predicting factors Elsevier Ireland Ltd. All rights reserved. Keywords: Follicular lymphoma; bcl-2; FLIPI; rituximab; t(14 ;18) 1. Definition, incidence and risk factors Follicular lymphomas are defined as a group of malignancies composed of follicle center cells, usually a mixture of centrocytes (cleaved cells) and centroblasts (large noncleaved cells). Diffuse areas may be present and, in fact, may even predominate, but follicles exist. This group of lymphomas includes many cases formerly recognized as centroblastic/centrocytic follicular or follicular centroblastic according to the Kiel classification [1,2] and follicular, small cleaved, mixed or large cell according to the Working Formulation classification. The term follicular lymphoma encompass most malignancies classified as nodular lymphomas in Working Formulation, most tumors classified as follicular center cell lymphoma in the Lukes-Collins classification, all cases in the Kiel classification category of centroblastic/centrocytic with any follicular pattern, and follicular centroblastic lymphoma [3]. The REAL classification [3] and more recently the WHO classification [4] proposes the term follicle center lymphoma, follicular grades 1, 2, 3a and 3b to distinguish predominantly small cell, mixed small- and large-cell, and large cell, respectively. Grades 1, 2 and 3a are treated similarly, while grade 3b disease is treated the same as diffuse large B-cell lymphoma. These lymphomas have been postulated as arising from a germinal center B-cell, both centrocytes (small cleaved follicular center cells) and centroblasts (large non-cleaved follicular center cells) [5 7]. Follicular lymphomas constitute the 30 35% of all NHL. Grade 1 follicular lymphoma is the 20 25%, grade 2 the 5 10% and grade 3 the 5% of all NHLs in the Western countries. These rates exhibit marked geographical variations. The cause and risk factors of follicular lymphomas are unclear. Although environmental and occupational exposures, such as exposure to solvents and chemical, have been implicated in the etiology of the disease. 2. Pathology and biology 2.1. Morphology Follicular lymphomas are characterized by at least partially follicular growth pattern, but diffuse areas may be present [2]. Sclerosis is common in diffuse areas. Centrocytes typically predominate; centroblasts are usually in the minority, but by definition are always present. Rare lymphomas with a follicular pattern consist almost entirely of centroblasts; because the follicular pattern implies a germinal center origin, these cases have been included in the category of follicular center cells lymphomas. Both the proportion of centroblasts and the size of the centrocytes vary among cases. This group of lymphomas should not be divided into distinct subtypes, but rather shows a continuous gradation in the number of large cells. On the bases of this grading, three groups have been defined: grades 1 3 [3]. Several studies suggest that the Berard criteria for the diagnosis of grade 3 follicular lymphoma (>15 centroblasts/high-power field) may best define the group of cases with a potential for early relapses that may be prevented by anthracycline-containing chemotherapy [8]. There is a consensus that grade 3 follicular lymphomas, namely grade 3b, should be discriminated from lower-grade cases. Although there are minor differences in natural history and response to treatment between grades 1 and 2 follicular lymphoma, there is a consensus that these do not mandate different approaches to treatment and thus are not of great clinical importance. Nonetheless, there was concern that changing the nomenclature would potentially confusing and that a three-grade system should be retained [4]. The proportions of follicular or diffuse areas vary also from case to case, which seems to be associated with prognosis. The pattern in a given case is reported as follicular or follicular and diffuse. Diffuse areas should be reported and quantified according to the recommendations of the REAL classification, i.e. predominantly follicular (>75% follicular), follicular and diffuse (25 75% follicular) and predominantly diffuse (<25% follicular). In grade 3 follicular lymphoma, diffuse areas represent areas of diffuse large cell lymphoma and should be reported as such, that is as follicular lymphoma grade 3/3 (75%) with diffuse large cell lymphoma (25%). For the rare cases of purely diffuse lymphoma that seems to be of follicle center origin, that is with predominance of centrocytes, rare centroblasts and bcl-2 rearranged, the term follicle center lymphoma, diffuse, will be retained as a separate category. This diagnosis should only be made if both small and large cells are B cells and preferably with demonstration of some indicator of follicle center

3 250 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) derivation, such as bcl-2 rearrangement or CD10 expression [4] Immunophenotype The cells of follicular lymphomas express surface immunoglobulin, more frequently IgM +/ IgD > IgG > IgA, B-cell-associated antigens (CD19, CD20, CD22, CD79a and CD79b), CD10+/. They are CD5, CD23 /+, CD43, and CD11c. CD5 and CD43 negativity is useful in differential diagnosis with chronic lymphocytic leukemia and mantle cell, while CD10 reactivity is useful in distinguishing follicular lymphomas from marginal zone lymphomas. Follicular lymphomas express bcl-2 proteins, which is useful in distinguishing reactive from neoplastic follicles [9,10] Genetic features t(14;18) is present in 70 95% of follicular lymphomas, involving rearrangement of bcl-2 gene [11 13]. This results in the expression of an anti-apoptosis gene, and the expression of the bcl-2 protein permits accumulation of long-lived centrocytes [14 16]. This translocation occurs at an early stage of B-cell development, during Ig gene rearrangement [16,17], being occasionally present in normal individuals [18,19]. Thus, when a resting B-cell that carries the bcl-2 translocation undergoes blast transformation in response to antigen, failure to switch off the bcl-2 gene may contribute to development of a lymphoma. 3. Clinical presentation and natural history Although not uncommon in the third and fourth decades, follicular lymphomas occur most commonly in middle-aged patients and elderly [20,21]. Every anatomic district may be involved, but the most common presentation is multiple lymphadenopathy, with or without abdominal or mediastinal masses, splenomegaly, hepatomegaly, and marrow involvement. Leukemic phase is less common than for other indolent lymphomas, and extranodal sites are usually involved with e lower frequency respect to diffuse large cell lymphomas. Clinical presentation and behavior of follicular lymphoma differ according to its histologic grade. Follicular lymphoma presents as advanced disease in 80 85% of grade 1 cases, in 70 75% of grade 2 cases and in 65 70% of grade 3 cases. Systemic symptoms are observed in 20% of grades 1 2 cases, and in 30% of grade 3 cases. Bone marrow involvement is observed in 50% of grade 1 cases and in 30 35% of grades 2 3 cases. Clinical behavior of follicular lymphomas is heterogeneous and differs according to the histologic grade and extension of disease at presentation. Moreover, the evaluation of these malignancies is conditioned by therapeutic decision, which is also determined by main prognostic factors. Similarly than for other indolent lymphomas, follicular lymphomas are considered fatal malignancies with conventional treatments. With time, these lymphomas often transform into a more aggressive histologic malignancy. Twenty-eight to 44% of patients with repeated biopsy during the course of the disease may show evidence of high-grade transformation [20,22 24]. Actually, this rate arises up to 70% in cases examined at autopsy [25,26]. These transformed lymphomas are usually quite aggressive and poorly responsive to chemotherapy [20,27]. In the largest reported series, a median survival of 22 months has been reported, while patients with high-grade transformed follicular lymphomas but limited stage disease showed a median survival of 81 months [28]. The risk of transformation is higher in patients with advanced stage, high-risk Follicular Lymphoma International Prognostic Index (FLIPI), and IPI scores at diagnosis. Expectant management (as opposed to treatment being initiated at diagnosis) also predicts for a higher risk of transformation [29]. Older age, low hemoglobin level, high lactate dehydrogenase (LDH), and high-risk FLIPI or IPI score at the time of first recurrence are associated with the diagnosis of transformation in a biopsy performed at that time. The median survival from transformation is about 1 year [29]. 4. Staging 4.1. Staging procedures Complete staging work-up for follicular lymphomas is the same that routinely used for other NHL. It includes an accurate physical examination, complete hematological and biochemical exams, total-body computerized tomography, and bone marrow aspirate and biopsy. Bone marrow assessment in follicular lymphoma should follow the general statements for all NHL. Abdominal staging, with evaluation of potential hepatic or splenic involvement in follicular lymphomas should follow the general statements for all NHL. Some particular sites of disease frequently involved by follicular lymphomas require especial diagnostic procedures. If clinically indicated, gastrointestinal tract radiological and endoscopic assessment, ultrasonography of the neck and magnetic resonance imaging of the orbits and soft tissues are useful to investigate the involvement of these anatomical regions Staging system The standard staging system used for follicular lymphomas is the same as that proposed for Hodgkin s lymphoma at the Ann Arbor Conference in 1971 [30]. This system is currently used for all non-hodgkin s lymphomas, even if other staging systems are used in some extranodal lymphomas with particular biological behavior. The Ann Arbor staging system reflects both the number of sites of involvement and the pres-

4 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) ence of disease above or below the diaphragm. This staging system considers four stages of disease: Stage I: involvement of a single lymph node region (I) or a single extranodal site (IE). Stage II: involvement of two or more lymph node regions on the same side of the diaphragm (II) or localized involvement of an extralymphatic site (IIE). Stage III: involvement of lymph nodes regions on both sides of the diaphragm (III) or localized involvement of an extralymphatic site (IIIE) or spleen (IIIs) or both (IIIEs). Stage IV: diffuse or disseminated involvement of one or more extralymphatic organs with or without associated lymph node involvement. Localized involvement of liver or bone marrow is also considered stage IV. Patients are divided in two subsets according to the presence (A) or not (B) of systemic symptoms. Fever of no evident cause, night sweats and weight loss of more than 10% of body weight are considered systemic symptoms. Even if a frequent accompanying symptom, itch should not be considered as a systemic symptom. The presence of bulky mass, such as a lesion of 10 cm or more in the longest diameter is signaled as X, while the extranodal involvement should be identified by a symbol (O: bone, L: lung, D: skin, etc.) Molecular analysis of minimal residual disease Molecular monitoring of minimal residual disease in follicular lymphoma provides an early endpoint to assess the curative potentiality of novel chemotherapy approaches and predicts relapse considering its sensitivity to detect tumor cells contained in the graft in autographing programs. Minimal residual disease in follicular lymphoma is currently detected by polymerase chain reaction (PCR), analysing the rearrangement of bcl-2 (see Section 2.3). This rearrangement is detectable in 60 80% of patients with follicular lymphoma. PCR amplification and sequencing of IgH genes is an alternative strategy in bcl-2-negative cases. The rearrangement of variable, diversity and joining segments of IgH genes generates unique DNA sequences that are clone-specific. These sequences are named complementary-determining regions (CDR) and code for the antigen-binding site [31]. Clonespecific primers and probes can be obtained from CDR sequences and used for the PCR detection of residual lymphoma cells. Comprehensively, the bcl-2/igh translocation and clonally rearranged IgH genes provided molecular markers for detection and follow-up of minimal residual disease by PCR amplification in several cases. Several prospective studies documented that the achievement of a sustained molecular response after conventional chemotherapy with or without rituximab was a favourable prognostic factor and correlated with prolonged failure-free survival (FFS) [32,33]. Serial PCR analysis to determine the molecular response correlates well with outcome [34,35] (see Section 5). 5. Prognostic factors Several groups have described prognostic factors for patients with advanced follicular lymphoma [36 38]. In the Groupe d Etude des Lymphomes Folliculaires schema, patients with any one of the following features are considered to have a high tumor burden: systemic symptoms, elevated LDH serum levels, bulky lesion >7 cm, effusion, three or more Ann Arbor sites each 3 cm or greater, circulating lymphoma cells, cytopenias, and splenomegaly [39,40]. The International Prognostic Index for aggressive lymphomas has been applied to follicular lymphomas and found to identify subgroups with significantly different prognosis [41 43]. However, only a small percentage of patients full into the higher risk group, such that this system of stratification may not be optimal for follicular lymphoma. In contrast, the International Prognostic Index showed a significant efficacy to identify risk groups in patients with follicular large cell lymphoma (grade 3) [44]. In these patients, age, stage, LDH ratio, 2-microglobulin level, and bone marrow involvement seem to play an independent prognostic role. In a series of 398 patients of the British National Lymphoma Investigation group, the Ann Arbor staging classification fared poorly, minimally separating relapse-free and cause-specific survival probabilities in patients with the largest staging grouping, III and IV. Increasing number of lymph node regions involved, systemic symptoms, splenomegaly and increasing age have been reported to have powerfully independent adverse influence on probability of complete response to treatment and cause-specific survival [45]. Molecular response, tested as PCR analysis of the rearrangement of bcl-2 in blood and marrow, is significantly related to event-free-survival in patients with follicular lymphoma treated with anthracycline-containing chemotherapy, with or without fludarabine, and with or without rituximab [32,34]. Serial PCR analysis to determine the molecular response correlates well with outcome, especially when combined with pretreatment 2-microglobulin level. The number of bcl2+ circulating cells decreases with autologous stem cell transplant (ASCT) [46] and patients with a molecular response after ASCT have a lower risk of relapse [35,47], the chance of relapse being proportional to the quantity of PCR positive cells found in peripheral blood. A negative PCR status post-transplant also reduced the chance of death and was more relevant onto overall survival (OS) than the PCR status of the reinfused graft [48]. Some chromosomal abnormalities with prognostic value in terms of risk or high-grade transformation and survival have been reported [49]. The presence of sclerosis within the lymphoma seems to be a marker of poor overall survival that is independent of the FLIPI [50]. High serum 2-microglobulin level [51], chromosomal abnormalities involving 6q23-26 and 17p [49], alterations or mutations of c-myc and p53 [52 54], and deletions of p15 and p16 [55 57] have been associated with an increased risk of high-grade transformation.

5 252 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) Due to the lack of prognostic system specifically devised for follicular lymphomas, in the last few years, two specific prognostic scores have been developed based on large series of patients treated in the last 15 years with mainly pre-rituximab treatments: the Italian Lymphoma Intergroup Index (ILI) [58] and more recently, the Follicular Lymphoma International Prognostic Index (FLIPI) [59]. Six variables were used to construct ILI index, three of them also being included in IPI (age, extrandal involvement and LDH level). The other three variables considered were presence of B- symptoms, male sex and erythrocyte sedimentation rate >30 mm/h. Patients were classified into low-, intermediateor high-risk groups, each of them with significantly different 5 and 10 years overall survival: 90 and 65% for patients at low risk; 75 and 54% for patients at intermediate risk; and 38 and 11% for those at high risk. Characteristics of diagnosis were collected from 4167 follicular lymphoma patients to construct FLIPI. The variables used to classify patients according to the FLIPI were age 60, advanced stages (III IV), increased serum LDH, hemoglobin level <12 g/dl and nodal involvement (five or more sites). Three risk groups were considered with different 5 and 10 years survival: score 0 1, low risk (90.6 and 70.7%); score 2 intermediate-risk (77.6 and 50.9%); and score 3, highrisk (52.2 and 35.5%). It is recommended to use one of these specific indexes to classify follicular lymphoma patients [60]. 6. Treatment 6.1. Watch and wait policy Treatment can be safely deferred without disadvantage on survival for patients with follicular lymphoma in stages III IV disease [24], provided that none of the following features occurs: systemic symptoms, high tumor burden, extranodal disease, cytopenia due to marrow involvement, spleen involvement, leukemic phase, serous effusion, high LDH levels. This watch and wait policy was evaluated by three trials that randomized to either chemotherapy or watchful waiting (WW) strategy patients with de novo, asymptomatic, advanced stage and a low tumor burden indolent lymphomas. Two old trials compared WW with ProMace-MOPP polychemotherapy [61], prednimustine or interferon [39], in stages II IV patients, and did not show any significant difference in 4- and 5-year survival, respectively, except for a significant prolongation of FFS with polychemotherapy. A more recent randomized trial [62], with a 16-year median follow-up, reported that median OS was 5.9 years for oral chlorambucil versus 6.7 years (p = 0.84) for observation. Cause-specific survival was also similar in the two arms: 9 years versus 9.1 years, respectively. The median time to first systemic treatment was 2.7 years in the WW group. Delay of treatment until significant clinical progression does not seem to hamper the prognosis or subsequent response to treatment. Patients with low-grade and limited disease follicular lymphomas should not be managed with a frontline WW strategy because these patients can obtain a long-term survival when treated with involved-field irradiation (IFRT) [63,64] Treatment of stages I II low-grade follicular lymphoma Standard therapeutic option for patients with stages I II grades 1 2 follicular lymphoma is matter of debate. However, there is sufficient evidence-supporting IFRT is suitable for individual clinical use on a type 3 level of evidence [64 66]. IFRT is most commonly used in localized lymphomas and implies treatment to the nodal region or extranodal sites and, if involved, its immediate lymph node drainage area. A treatment plan including the adjacent, second echelon not involved lymph nodes is usually considered extended field RT, even if a true extended field is referred to the classical Hodgkin s fields. Patients with stages I and II follicular lymphoma treated with a radiation dose of Gy delivered in fractions over 2 4 weeks experienced local control rates of more than 95%, while there is insufficient information to assess the impact of doses lower than 30 Gy on local control. Moreover, radiation therapy alone achieved an excellent survival and long-term disease control. In a recent update of the Princess Margareth Hospital experience, OS at 5 and 10 years was 79 and 62%, while DFS was 56 and 41%, respectively [67]. In a retrospective study, 43 untreated patients with stages I and II follicular lymphoma deferred initial therapy for various reasons. Only 16 (37%) patients received a treatment within 7 years from the diagnosis, with a 10-year OS was 85%. Patients with stage I disease without residual lymphoma after excisional biopsy, may attain a very good outcome despite no further treatment and adjuvant radiotherapy seems to be unnecessary [68,69]. Some authors reported improved results with the addition of primary chemotherapy to radiation therapy [70]. A 5-year OS and FFS of 89 and 74% have been reported in 44 patients treated with cyclophosphamide, vincristine, bleomycin, and prednisone, with or without doxorubicin [70]. However, six randomized level I II trials reported that the adjunct of chemotherapy to first-line radiotherapy does not prolong patients survival in stages I II follicular lymphoma patients [71,72]. An innovative approach in the treatment of localized stage disease with low tumor burden might be the association of immunotherapy (rituximab) to radiotherapy. So far, no studies comparing radiotherapy alone to combination radiotherapy and rituximab have been reported Treatment of stages I II with high tumor burden and/or high-risk follicular lymphoma Within the subset of patients with limited stages I II disease, high tumor burden and high-risk (IPI > 1, ILI > 2) were

6 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) considered negative predictors of progression-free survival in three phase II studies [73 75]. Frontline chemotherapy followed by IFRT is suitable for individual clinical use in stages I II patients with a high tumor burden. With this strategy, 5-year FFS and OS are and 70 75%, respectively Treatment of stages III IV follicular lymphoma A univocal standard therapeutic option for patients with stages III IV low-risk follicular lymphoma does not exist. The role of extended field radiotherapy alone has been evaluated in stage III follicular lymphomas in three retrospective studies [65,76,77]. The subset of patients with limited stage disease (defined as fewer than five disease sites, tumor masses less than 10 cm and no B symptoms), showed a better outcome, i.e. FFS of 88% at over 23 years followup. However, the risk of secondary cancers with extended radiotherapy/central lymphatic irradiation, as compared with chemotherapy alone, is high and extended radiotherapy should not be considered a valuable first-line therapy in patients with advanced disease. The choice of optimal chemotherapy is still a matter of debate. Many randomized trials compared different regimens of chemotherapy in advanced stage indolent lymphomas: alkylating agents, anthracycline-based chemotherapies, purine analogs, and CVP-like regimens. Single agent chemotherapy with chlorambucil or cyclophosphamide was widely used in advanced stage indolent lymphomas with an overall response rate of 54 72%, a complete remission rate of 30 70%, and a median OS ranging from 4.5 to 9 years [78]. Single-agent chemotherapy was compared to polychemotherapy like CVP or anthracyclinecontaining regimens. Although some studies reported a higher response rate with polychemotherapy, none was able to show a better outcome compared to single-agent chemotherapy [79 81]. Even if well tolerated, chlorambucil should be avoided in young patients with follicular lymphoma considering that long-term exposure to cumulative alkylating dose may induce impairment of peripheral blood stem cell mobilization and a higher risk of secondary myelodysplasia. CVP combination regimen (cyclophosphamide, vincristine and prednisone) shows equivalent efficacy to monochemotherapy. Several prospective and retrospective studies reported outcomes of first-line therapy with CHOP in overall patients [82]. A superior outcomes with CHOP as compared with CHOP-like regimens or with CVP-like regimens has not been confirmed so far [80,83]. Fludarabine single-agent therapy was shown to be effective in indolent lymphoma with an overall response rate of 60 70% and complete remission rates of 30 37% [84]. In an EORTC randomized trial, fludarabine showed significantly better overall and complete response rates than CVP; however, both time to progression and OS did not differ between the two arms [85]. Fludarabine-containing regimens with mitoxantrone ± dexamethasone were able to induce an overall response rate from 81 to 94% and a 4-year PFS near of 20 38% [86,87]. This regimen was recently shown to give a higher complete remission and molecular response rates than CHOP chemotherapy regimen in a randomized trial, although no survival benefit has been reported so far [88]. The addition of interferon-alfa 2b to primary chemotherapy was tested in randomized trials. In a meta-analysis of eight randomized trials, a significant improvement in 5-year OS and PFS was reported [89], but in a subsequent metaanalysis based on individual-patient data from 10 randomized trials [90], interferon addition to initial chemotherapy did not significantly improve the response rate, however, interferon significantly improved OS only when associated with a dose higher than 5 million units and a cumulative dose over 36 million units. At least on third of the patients treated with interferon combination therapy dropped out due to severe fatigue or toxicity. Taking into account toxicity and costeffectiveness analysis, the combination of interferon and chemotherapy dose not balance a possible survival benefit. Chimeric anti-cd20 antibody (rituximab) is effective in relapsed or refractory follicular lymphomas [91,92]. Rituximab single-agent was also used in untreated patients with indolent lymphomas with stages III IV disease and low tumor burden. Overall response rates ranged from 72 to 100% and molecular response in peripheral blood was 53%. Oneyear PFS ranged from 69 to 80% and was from 32 to 49% at 3 years. Ongoing studies are comparing the efficacy of WW strategy or radiotherapy with that of rituximab monotherapy in this subset of patients. Combination of rituximab to chemotherapy, either concurrent or sequential, has been proved to be effective in advanced stage follicular lymphoma who required treatment [33,93 95]. Four randomized studies, enrolling more than 1000 patients, recently provided evidence on the efficacy of rituximab combined with CVP, CHOP, MCP or CHVP + IFN regimens in advanced stage follicular lymphoma [96 99]. The addition of rituximab to first-line chemotherapy (CVP or CHOP) significantly increased overall response rates and prolonged time to treatment failure in both studies. A survival benefit was also shown with CHOP and rituximab compared to CHOP alone [97]. There is a strong evidence (type 1) on the benefit of adding rituximab to chemotherapy and the combination of rituximab to any type of conventional chemotherapy regimens should be considered the standard care as firstline treatment in advanced stage follicular lymphoma who required treatment [83]. The choice of chemotherapy largely depends on many factors such as: patient s age and performance status, comorbidity, the pace of disease, and the aim of the treatment, i.e. palliation or attempt to cure Treatment of stages III IV high-risk follicular lymphoma Standard option in stages III IV high-risk (IPI > 2, ILI > 2, FLIPI > 2) follicular lymphoma has not been yet established. Conventional chemotherapy with the addition of

7 254 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) rituximab should be regarded as the standard treatment also in these patients outside clinical trials. The use of high-dose chemotherapy (HDC) supported by ASCT as consolidation treatment in patients who achieved a remission after primary chemotherapy is an investigational option tested in phase II studies [47,100]. With this approach a high overall and complete response rate has been reported with a 3-year PFS ranged from 40 to 65% and many patients achieved molecular remission; however, the inclusion criteria differed between the trials and patients were not always selected as highrisk ones. The effectiveness of fontline HDC supported by ASCT has been recently tested in randomized phase III studies by the GOLEAMS and GLSG study group [101,102]. The German Low-grade Study Group (GLSG) trial showed that consolidation with myeloablative radiochemotherapy followed by ASCT, after CHOP-like therapy, compared to conventional interferon maintenance, prolonged PFS in 307 patients with follicular lymphoma in first remission [102]. The GOLEAMS 064 trial, however, did not report a significant advantage in OS of ASCT at 56 months of median follow-up, while 5-year event-free survival increased from 48 to 60% [101]. In a randomized comparison on 401 treatmentnaive patients with advanced follicular lymphoma, there was not difference in terms of event-free or OS between standard CHVP chemotherapy regimen (cyclophosphamide, doxorubicin, teniposide, and prednisone) plus interferon and 4 courses of CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) followed by HDC with ASCT [103]. These observations seem to suggest that HDC should be reserved for relapsing patients. None of these studies showed a plateau in survival curves after HDC plus ASCT and no definite data are available comparing this approach with frontline chemoimmunotherapy. Such studies are ongoing and high-risk follicular lymphoma patients younger than 60 years should be encouraged to be enrolled into prospective clinical trials testing this approach compared to standard chemoimmunotherapy Maintenance treatment of stages III IV follicular lymphoma The role of interferon maintenance therapy has been tested in many trials with conflicting results. A recent metaanalysis [90] analysed 10 randomized trials and concluded that interferon could not improve OS when administered as a maintenance therapy. Moreover, long-term interferon therapy severely impairs patients quality of life and such detrimental effect may offset the potential clinical benefit. Preliminary results supported the positive role of maintenance rituximab infusion on response duration in follicular lymphoma patients [104]. A Swiss trial showed that prolonging rituximab monotherapy for four to eight doses induced a prolongation of median event-free survival in 185 patients with follicular lymphoma, from 12 to 23 months [105]. The benefit of maintenance rituximab after first-line chemoimmunotherapy has not yet been demonstrated and the safety of long-term administration of rituximab has not been fully evaluated. Rituximab maintenance treatment is still an investigational approach and the real long-term benefit of rituximab in this setting should be tested in more randomized studies with adequate followup Treatment of relapsed or refractory follicular lymphoma Histopathological transformation to large cell aggressive lymphoma occurs frequently in the course of follicular lymphoma, especially within the first 6 years from diagnosis [51] and they have a dismal prognosis (see below). Therefore histopathological reassessment is mandatory before any treatment decision in relapsed patients. Standard treatment in relapsed or refractory follicular lymphoma is controversial. It depends on prior treatment, duration of the time-to-relapse, patient s age, and histological findings at relapse. To use again the same strategy used as first-line treatment is suitable for individual clinical use on a type R basis in aged patients with a long timeto-relapse and without high-grade transformation. Patients who did not respond to or relapsed after alkylator singleagent as first-line therapy might benefit of an anthracyclineor fludarabine-based chemotherapy associated with rituximab. Purine analogs, mainly in association, are suitable for individual clinical use on a type 3 basis in patients relapsed after primary anthracycline-containing chemotherapy. Excellent results have been reported with fludarabine, which produces a response rate of 50% in relapsed cases [86,106], and prospective evidence supports the use of rituximab. In refractory/relapsed patients, rituximab monotherapy achieved overall response rates of 48%, but complete remission rate was only 6%. The median duration of response is shorter than 1 year [92]. Association of rituximab with chemotherapy is much more effective than singleagent therapy. In phase II studies enrolling patients with relapsed/resistant follicular lymphoma, the association of CHOP-like or fludarabine-based polychemotherapy with rituximab gave an overall response rate ranging from 82 to 97%. Moreover, chemoimmunotherapy (with rituximab) achieved molecular response in 70 90% of bcl2-positive patients; elderly patients did not achieve lower response rates than the younger patients [94]. A randomized trial in patients with relapsed and refractory follicular lymphoma reported a prolonged PFS with the addition of rituximab to fludarabine, cyclophosphamide and mitoxantrone (FCM regimen) compared to FCM alone [107]. HDC supported by ASCT was shown to be superior to standard chemotherapy in retrospective controlled studies [35,48, ] and in a randomized trial [111]. The CUP trial [111], comparing standard chemotherapy (CHOP) to HDC + ASCT in relapsed follicular lymphoma showed a nearly 50% reduction of relapse rate and a statistically sig-

8 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) nificant improvement of PFS and OS by ASCT. Status of disease at transplant is the best predictor for outcome: in 419 follicular lymphoma patients undergoing ASCT, 12-year OS and disease-free survival was 61 and 37% and transplantation in second remission increased the risk of being disease-free by 2.3 [112]. Therefore, HDC with ASCT is advisable in relapsed patients who achieved a response to re-induction chemotherapy. In a recently reported retrospective study [113], histological grade 3, high-risk FLIPI score at the time of transplantation, and three or more previous chemotherapy regimens were significant factors for predicting a worse outcome. In addition, the use of a transplantation regimen including a monoclonal antibody decreased the relative risk of progressive lymphoma. These data suggest that transplantation earlier in the course of the disease for patients with follicular lymphoma with use of a monoclonal antibody-based regimen, may lead to improved outcomes. The major long-term complications of ASCT were secondary myelodisplatic syndrome (smds), occurring in 3 15% of patients at 5 years after transplantation [ ]. However, in a report of the EBMT Working Party on almost 5000 lymphoma patients, the incidence of smds was only 3% [115]. Total-body irradiation conditioning was reported to increase the incidence of smds by up to fivefold and should be avoided [117]. Recently, conditioning strategies for ASCT have incorporated radioimmunoconjugate (tositumobab or ibritumobab) regimens suggesting a better outcome compared with retrospective cases [118]. However, prospective controlled studies are still lacking. Lymphoma cells often contaminate bone marrow and peripheral blood stem cell collections and may contribute to relapse after ASCT. More recently, in vivo purging was achieved by administering rituximab prior to ASCT. Three-year relapse-free survival and 2-year PFS were 84% and 97%, respectively, in the most recent studies [119]. A negative PCR status posttransplant also reduced the chance of death and was more relevant onto OS than the PCR status of the reinfused graft [48]. Allogeneic bone marrow transplantation is also an investigational option, which has been associated with a 3-year OS of 49% in high-risk relapsed patients [120,121]. Allogeneic SCT proved to have a high benefit-to-risk ratio, especially in chemosensitive young patients with excellent PS [121]. A high number of trials indicate that long-term molecular remission are frequent, and a survival plateau in patients alive at 2 years from transplant was reported. In patients with no response to standard chemotherapy the chance of failure even with HDC and ASCT is high and these young patients, if a sibling donor is available, may benefit from allogeneic SCT. The incidence of post-transplant smds/aml is very low [122]; however, allogeneic SCT has an overall transplant-related mortality (TRM) of about 20% at the latest reports [122,123], this complication was higher in chemorefractory patients. An attempt to reduce TRM is the use of reduced intensity conditioning regimens in allogeneic transplantation. No randomized trial supported the superiority of reduced intensity conditioning over conventional conditioning, although TRM data retrospectively collected in mixed NHL cohorts would suggest it [ ]. The role and place of allogeneic SCT in follicular lymphoma needs to be better defined, however, the low relapse rate after allogeneic transplantation is strongly suggestive for the existence of a graft-versus-low-grade lymphoma effect. Radioimmunotherapy (RIT) is a relative new approach to follicular lymphomas and is another therapeutic option in patients not responding to or relapsing after first-line chemotherapy. RIT is effective in relapsed patients also outside a transplantation procedure [127]. Beta-emitting anti-cd20 antibodies, i.e. ibritumomab, achieved 60 70% overall response rate and 20 35% CR [128,129]. Durable responses were shown at long-term follow-up in large cohorts of patients with relapsed/refractory follicular lymphoma treated with ibritumomab, tiuxetan or tositumomab. Complete responders kept the response status for over 24 months and median response duration was longer than for the previous line of therapy. 90 Y-ibritumomab was also more effective than rituximab single-agent in a randomized trial [130]. Myelotoxicity is the most common adverse effect of these treatments with grade 4 neutropenia occurring in 5 35% of the patients and grade 4 thrombocytopenia occurring in 3 16%. However, serious infections were rare occurring in 5 7% of the patients [131]. The risk of severe complications increased in patients with bone marrow involvement. Long-term complications of RIT included smds, however, the actuarial risk is less than 1.5%, which is not different from the risk observed after chemotherapy [128,132]. This therapeutic modality has substantial promise for the future, either alone or in alternative to total-body irradiation as conditioning regimen for ASCT or as an adjunct to chemotherapy Treatment of high-grade transformed follicular lymphoma The prognosis for high-grade transformed lymphoma is generally poor, being median survival from transformation about 10 months [51], thus, accounting for a large proportion of mortality in patients with follicular lymphomas. Standard management for high-grade transformed follicular lymphomas is the same as for diffuse aggressive lymphomas. Outcome in transformed NHL treated with standard chemotherapy was poorer than for de novo diffuse large B-cell lymphoma. Age, response to salvage therapy, B symptoms, LDH values, bone marrow involvement, stage, no prior chemotherapy, and early transformation were all predictive factors for survival after transformation [51,133]. HDC and ASCT are advisable in young patients who respond to chemotherapy. Median OS from ASCT was reported to be 40 60% at 4 5 years [133,134] and 5- year DFS was about 30% in over 200 patients included in published series [135]. Survival after ASCT was similar to that reported for nontransformed indolent NHL and

9 256 U. Vitolo et al. / Critical Reviews in Oncology/Hematology 66 (2008) primarily aggressive NHL undergoing ASCT. In refractory cases, HDC supported by allogeneic transplantation is an investigational option, may having something to offer in the setting of selected younger patients with a compatible marrow donor [136]. High overall response rates, ranging from 50 to 80%, and an acceptable safety were reported in transformed patients with a bone marrow involvement <25% treated with radioimmunotherapy, ibritumomab and tositumomab [128,137]. For the subset of patients with both the bcl-2 and the c-myc translocations, the results appeared to be particularly poor and no effective regimen was reported [138] New drugs and combinations in follicular lymphoma Several investigational approaches are currently under investigation in phase II trials. Some forms of immunotherapy like idiotypic vaccinations against human B-cell lymphoma are being explored [ ]. Immunization with patientand tumor-specific vaccines using idiotypic proteins as immunogen has been applied in patients in first or second complete remission, obtaining a specific anti-idiotypic immune response in half of cases [142]. Median time to progression in patients who developed an immune response was 7.3 years, in comparison to 1.3 years for those without immune response. This difference seems to be associated with a survival advantageous. An 18-base phosphorothionate-stabilized antisense oligonucleotide that is complementary to the first six codons of the bcl-2 mrna has been administered to five patients with follicular lymphoma [143]. The aim of that trial was to restore apoptosis blocking the expression of bcl-2 gene. One complete remission and one minor response were seen. Larger phase II trials are currently developed. 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