VAC Protocol for Treatment of Dogs with Stage III Hemangiosarcoma

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1 RETROSPECTIVE STUDIES VAC Protocol for Treatment of Dogs with Stage III Hemangiosarcoma Francisco J. Alvarez, DVM, MS, DACVIM, Kenji Hosoya, DVM, MS, DACVR, DACVIM, Ana Lara-Garcia, DVM, MS, PhD, DACVIM, MRCVS, William Kisseberth, DVM, MS, PhD, DACVIM, Guillermo Couto, DVM, DACVIM ABSTRACT Hemangiosarcomas (HSAs) are aggressive tumors with a high rate of metastasis. Clinical stage has been considered a negative prognostic factor for survival. The study authors hypothesized that the median survival time (MST) of dogs with metastatic (stage III) HSA treated with a vincristine, doxorubicin, and cyclophosphamide (VAC) chemotherapy protocol would not be different than those with stage I/II HSA. Sixty-seven dogs with HSA in different anatomic locations were evaluated retrospectively. All dogs received the VAC protocol as an adjuvant to surgery (n ¼ 50), neoadjuvant (n ¼ 3), or as the sole treatment modality (n ¼ 14). There was no significant difference (P ¼ 0.97) between the MST of dogs with stage III and stage I/II HSA. For dogs presenting with splenic HSA alone, there was no significant difference between the MST of dogs with stage III and stage I/II disease (P ¼ 0.12). The overall response rate (complete response [CR] and partial response [PR]) was 86%). No unacceptable toxicities were observed. Dogs with stage III HSA treated with the VAC protocol have a similar prognosis to dogs with stage I/II HSA. Dogs with HSA and evidence of metastases at the time of diagnosis should not be denied treatment. (J Am Anim Hosp Assoc 2013; 49: DOI /JAAHA-MS-5954) Introduction Hemangiosarcoma (HSA) is a malignant neoplasm that is thought to originate from either endothelial cells or their precursors. 1 3 It is common in older dogs and comprises approximately 7% of all malignancies. 1,4 HSA occurs in dogs of any breed; however, German shepherd dogs and golden retrievers are at higher risk for this neoplasm. 4 6 The most common anatomic sites affected are the spleen, right atrium, liver, and subcutis; however, other organs and tissues, such as bone, kidney, bladder, skin, oral cavity, muscle, lung, peritoneum, aorta, pulmonary artery, and central nervous system can be affected. 1,2,7 9 Most HSAs are aggressive tumors with a high rate of metastasis and local tissue invasion. 9 The most common sites for metastases include liver, lung, peritoneum, muscle, lymph node, adrenal gland, and diaphragm. 2 Interestingly, dermal HSA has a lower metastatic potential than HSAs in other anatomic locations and dogs with dermal HSA have longer survival times than those with subcutaneous HSA. 4,10,11 In recent studies, it appears that subcutaneous and renal HSA may have longer survival times than splenic HSA; however, in another study including dogs with subcutaneous and intramuscular HSAs, a median survival time (MST) of 172 days was achieved, and only 25% dogs lived. 1yr Treatment of dogs with splenic HSA by splenectomy alone results in a MST of days. 2,5 Dogs with HSA (including those with subcutaneous HSA) treated with postoperative chemotherapy achieve a MST of days when treated with either doxorubicin as a single agent or doxorubicin as part of a combination protocol with cyclophosphamide or cyclophosphamide and vincristine. 1,3,15,16 In a recent study of doseintensified doxorubicin administered q 2 wk instead of q 3 wk, From Coral Springs Animal Hospital, Coral Springs, FL (F.A.); Hokkaido University, Graduate School of Veterinary Medicine, Hokkaido, Japan (K.H.); University of London, Royal Veterinary College, London, United Kingdom (A.L-G.); and The Ohio State University, College of Veterinary Medicine, Columbus, OH (W.K., G.C.). CR complete response; HSA hemangiosarcoma; MST median survival time; PD progressive disease; PO per os; PR partial response; SD stable disease; VAC vincristine, doxorubicin, and cyclophosphamide; WHO World Health Organization Correspondence: faberger@yahoo.com (F.A.) ª 2013 by American Animal Hospital Association JAAHA.ORG 1

2 dogs with clinical stage I, II, and III HSA had MSTs of 257 days, 210 days, and 107 days, respectively. 17 The MST for all dogs as a group was not reported. In general, clinical stage has been considered a negative prognostic factor for survival for dogs with HSA at any anatomic location, and most owners of dogs with stage III disease are discouraged from pursuing treatment. In the authors experience and in a recent study, it was shown that dogs with HSA and measurable disease may respond to chemotherapy, suggesting that any primary or metastatic HSA lesion may respond to chemotherapy. 18 The purpose of the study reported here, therefore, is to compare the survival times for dogs with stage III HSA and dogs with stage I/II HSA treated with the vincristine, doxorubicin, and cyclophosphamide (VAC) protocol. In this study, the authors hypothesize that the survival times for dogs with HSA treated with the VAC protocol would not be affected by clinical stage. Materials and Methods The medical records of all dogs with HSA diagnosed between 2000 and 2007 and treated with a modified VAC protocol alone or as postoperative adjuvant or as neoadjuvant treatment that completed at least one cycle of the protocol (i.e., intent to treat) and had follow-up evaluations at The Ohio State University Veterinary Medical Center were evaluated retrospectively. Dogs with HSA confined to the dermis were excluded. All dogs received chemotherapy and were treated with a sequential combination of the VAC protocol. The modified VAC protocol consisted of a 21 day cycle of doxorubicin (either 30 mg/m 2 or 1 mg/kg in dogs, 10 kg) IV on day 1, vincristine ( mg/m 2 IV on day 8 and day 15), cyclophosphamide ( mg/m 2 per os [PO] on day 10, and trimethoprim/sulfamethoxazole (15 mg/kg q 12 h for the complete cycle) as summarized in Table 1. Thus, it was modified from the VAC protocol previously reported in that the cyclophosphamide was given PO on day 10 at a slightly higher dose TABLE 1 Description of the VAC Chemotherapy Protocol Used in This Study Day 1 Day 8 Day 10 Day 15 Doxorubicin (30 mg/m2 IV) Vincristine ( mg/m 2 IV) Cyclophosphamide ( mg/m 2 PO)* Trimethoprim/sulfamethoxazole (15 mg/kg PO q 12 hr) *If hemorrhagic cystitis developed, the cyclophosphamide was discontinued and chlorambucil was instead prescribed at a dose of 20 mg/m 2 PO. PO, per os; VAC, vincristine, doxorubicin, and cyclophosphamide. rather than IV on day 1. 1 If hemorrhagic cystitis occurred, cyclophosphamide was discontinued and chlorambucil was administered PO at a dose of 20 mg/m 2. Physical examinations and complete blood counts were performed before each cycle. Toxicity data were collected from the medical records when a complete blood count and clinical history of gastrointestinal signs were reported; however, hematologic and gastrointestinal toxicities were assessed only to determine whether treatment was either delayed or the dose was reduced due to toxicity. Dogs were assigned to one of two groups. Group 1 had clinical stage III or metastatic disease and group 2 had clinical stage I/II or localized disease. Dogs were staged according to the World Health Organization (WHO) staging system for domestic animals. Stage I was a tumor confined to the primary site, stage II was a tumor. 5 cm or that had either ruptured or spread to the regional lymph node, and stage III was a primary tumor with either measurable metastasis or multicentric disease (Table 2). 19 Dogs with measurable disease were monitored for objective tumor response to chemotherapy according to the WHO criteria. 20,21 A complete response (CR) was defined as complete disappearance of all measurable tumors, a partial response (PR) was defined as $ 50% decrease in measurable disease from baseline, stable disease (SD) did not meet the criteria for CR or PR and minimum duration of. 6 wk, and progressive disease (PD) was either a. 25% increase in one or more tumors or the development of new tumors. Duration of overall response was determined from the date of starting chemotherapy to the date of identification of new metastatic lesions, PD, or death. 20 Response to therapy was monitored by physical examination before each treatment and by thoracic radiography, abdominal TABLE 2 Clinical TNM Staging System for Dogs with HSA TNM and stage T N M Description T 0 ¼ no evidence of tumor T 1 ¼ tumor, 5 cm confined to the primary site T 2 ¼ tumor $ 5 cm confined to the primary site T 3 ¼ tumor involving adjacent structures N 0 ¼ no lymph node involvement N 1 ¼ regional lymph node involvement N 2 ¼ distant lymph node involvement M 0 ¼ no distant metastasis M 1 ¼ distant metastasis Stages I ¼ T 0 or T 1 ;N 0 ;M 0 II ¼ T 1 or T 2 ;N 0 or N 1 ;M 0 III ¼ T 2 or T 3 ;N 0,N 1 or N 2 ;M 1 HSA, hemangiosarcoma; TNM, tumor, node, metastasis. 2 JAAHA 49:6 Nov/Dec 2013

3 VAC for Dogs with Stage III Hemangiosarcoma ultrasonography, and/or echocardiography at regular intervals. Survival times for the dogs with follow-up data were calculated from the time of diagnosis to death caused by the tumor. Dogs either lost to follow-up or that died of an unrelated cause were censored for the analysis at the time of the last visit or death. Statistical Analysis Statistical analysis was performed to compare the MSTs of dogs with stage III and stage I/II disease. Also, the MSTs of dogs with splenic stage III and splenic stage I/II HSA were compared. The influence of different factors on MST was compared, including gender, histopathologic grade, anatomic location of the primary mass, breed, treatment delays or dose reductions and site of metastases, and those factors were analyzed with Kaplan-Meier method. Differences between groups were analyzed using the log-rank test. Contingency tables using the Fisher exact test were used to analyze the difference between 1 yr survival rate of dogs with stage III and stage I/II disease. Statistical significance was established as P # All analyses were performed using a commercial software package a. Results During the study period, 179 dogs were diagnosed with HSA. Of those, 67 fulfilled the criteria for inclusion in this study. The primary anatomic location of those tumors included spleen (28 of 67; 42%), subcutis (17 of 67; 25%), bone (9 of 67; 13%), heart (5 of 67; 7%), liver (2 of 67; 3%), kidney (2 of 67; 3%), muscle (2 of 67; 3%), mediastinum (1 of 67; 1.5%), and retroperitoneum (1 of 67; 1.5%). Of the 28 dogs with splenic HSA, 8 (29%) had an echocardiogram performed and 2 of those 8 dogs (25%) had a concurrent mass in the right atrium at the time of diagnosis. One dog had evidence of diffuse pulmonary metastases and another dog had liver metastases. Both of those 2 dogs had a splenectomy performed prior to initiating chemotherapy. Echocardiography was performed in 4 of 5 dogs with right atrial location, and the mass was visualized in all 4 of those dogs. The 5th dog was diagnosed surgically, and the diagnosis was confirmed histopathologically. An echocardiogram was performed in 12 of 34 primary locations other than the spleen or right atrium, and none had evidence of a right atrial mass. The most common breeds were mixed-breed dogs (17 of 67; 25%), golden retrievers (15 of 67; 22%), Labrador retrievers (7 of 67; 10%), greyhounds (5 of 67; 8%), German shepherd dogs (4 of 67; 6%), rottweilers (3 of 67; 5%), cocker spaniels (2 of 67; 3%), and 14 other breeds (1 of each). The mean age of the 67 dogs was 9.3 yr (range, 4 mo to 15 yr). There were 31 females (29 spayed) and 36 males (29 castrated). Mean patient weight was 29.6 kg (range, 4 53 kg). The diagnosis was confirmed histopathologically in 61 dogs and cytologically in 4 dogs. Cytology/biopsy was not performed in 2 dogs with right atrial location; however, both dogs had evidence of pulmonary metastatic disease and were included in the study. Histopathologic grading was performed in 44 tumors available for review. Of those, 9 tumors (20%) were well differentiated, 20 tumors (46%) were moderately differentiated, and 15 tumors (34%) were poorly differentiated. Of the 67 dogs, 25 (37%) had evidence of metastases (stage III) and 42 dogs (63%) did not have evidence of metastases (stage I/II). Of the latter group, 14 dogs were clinical stage I and 28 dogs were clinical stage II. The most common sites of metastases were the lungs (12 of 25; 48%) and liver (7 of 25; 25%). Other sites of metastases were omentum/mesentery, adrenal glands, and pancreas. Of the 25 dogs with clinical stage III disease, 11 had a primary tumor in the spleen, 5 in the subcutaneous tissue, 4 in the right atrium, 2 in the kidney, 2 in the liver, and 1 in the bone. Of the 11 dogs with splenic HSA and evidence of metastases, the most common sites of metastases were the liver (5 of 11; 46%) and lungs (3 of 11; 27%). Lung was the most common site of metastasis for HSAs located in the right atrium, subcutaneous tissue, and other locations (2 of 4; 50%; 4 of 5; 80%; and 3 of 5; 60%, respectively). Fourteen of the 67 dogs (21%) received VAC chemotherapy as the only treatment modality (6 of 14 dogs with stage I/II, 8 of 14 dogs with stage III), and 50 of 67 dogs (75%) received postoperative adjuvant chemotherapy (33 of 50 dogs with stage I/II, 17 of 50 dogs with stage III). Three dogs received neoadjuvant chemotherapy followed by surgery. The median number of chemotherapy cycles was 4 (range, 1 8). The median number of cycles of the dogs that received either adjuvant chemotherapy after surgery and chemotherapy alone was 4 (range, 1 8) and 3(range,1 6), respectively. The MST for the 67 dogs was 189 days (range, days). The MSTs for dogs with stage III and stage I/II tumors were 195 days (range, days) and 189 days (range, days), respectively. There was no significant difference in MST between dogs with stage III and stage I/III disease (P ¼ 0.97) as shown in Figure 1. The MST for dogs with stage III splenic HSA was 195 days (range, days), whereas it was 133 days (range, days) for dogs with stage I/II splenic HSA (P ¼ 0.12) as shown in Figure 2. The overall 1 yr survival rate for the 67 dogs was 10%. The 1 yr survival rate for the dogs with clinical stage III and clinical stage I/II were 4% and 15%, respectively (P ¼ 0.15). The 1 yr survival rate for the dogs with stage III and stage I/II splenic HSA were 8% and 12%, respectively (P ¼ 0.72). There was a significant difference in MST between dogs that had metastasis in either the liver (n ¼ 7) or lung (n ¼ 12). The MST for dogs JAAHA.ORG 3

4 FIGURE 1 Survival times for dogs diagnosed with hemangiosarcoma (HSA) with stage III (195 days) and stage I/II (189 days) treated with a vincristine, doxorubicin, and cyclophosphamide (VAC) chemotherapy protocol ( P ¼ 0.97). with evidence of metastasis to the liver was 150 days, and the MST for dogs with metastatic disease in the lungs was 239 days (P ¼ 0.04). There was no significant difference in the MSTs between gender (P ¼ 0.48), histopathologic grade (grade 1, 2, and 3; P ¼ 0.97), breed (P ¼ 0.16), either treatment delays or dose reductions (P ¼ 0.84), or anatomic location of the primary mass (splenic versus subcutaneous; P ¼ 0.52) as shown in Figure 3. Evaluation of response to chemotherapy in patients with measurable disease was available in 28 dogs (19 with stage III, 9 with stage I/II). The overall response rate (CR and PR) was 86%, and the overall response rate for dogs with clinical stage III was 89%. Of those 28 dogs, 12 dogs (43%) achieved a CR (10 of 19 dogs [53%] with stage III, 2 of 9 dogs [22%] with stage I/II), 12 dogs (43%) achieved a PR (6 of 19 dogs [32%] with stage III, 6 of 9 dogs [67%] with stage I/II), 3 dogs (11%) had SD (2 of 19 dogs FIGURE 2 Survival times for dogs with stage III (195 days) and stage I/II (133 days) splenic HSAs treated with a VAC chemotherapy protocol (P ¼ 0.12). FIGURE 3 Survival times for dogs with splenic (140 days) and subcutaneous (210 days) HSAs treated with a VAC chemotherapy protocol (P ¼ 0.52). [11%] with stage III, 1 of 9 dogs [11%] with stage I/II), and 1 dog with clinical stage III had PD (Figures 4, 5). The MST for dogs that achieved a CR was 270 days (range, days, including 239 days for dogs with stage III). For dogs that achieved a PR, the MST was 115 days (range, days, including 139 days for dogs with clinical stage III). For dogs that had SD, the MST was 105 days (range, days). There was a statistically significant difference between the MSTs of dogs that achieved a CR, a PR, or had SD. Dogs with a CR had longer survival times than dogs with either a PR or SD (P ¼ 0.01), and there was no difference between dogs with a PR and SD. Evaluation of response was not available in 6 of 34 dogs. Two dogs had survival times of 28 and 27 days, respectively, and 4 dogs were lost to follow-up at 17 days, 33 days, 95 days, and 149 days. Of the 12 dogs with widespread pulmonary metastases, 11 were evaluated for response to chemotherapy. Of those, 7 dogs (64%) achieved a CR, 2 dogs (18%) had a PR, 1 dog had SD, and 1 dog had PD. The median number of cycles of VAC was 4 (range, 1 8). Chemotherapy was either delayed or the dose was reduced at least once during treatment in 36 of 67 dogs (53%). It was delayed in 12 of 67 dogs (18%) and the dose was reduced in 33 of 67 dogs (49%). Three of the 67 dogs (4.4%) developed evidence of hemorrhagic cystitis; therefore, chlorambucil (20 mg/m 2 ) was substituted for cyclophosphamide in those dogs. Two dogs (3%) developed sepsis during chemotherapy; however, no dog died due to sepsis. When recorded, the treatment was either delayed or the dose was reduced because of neutropenia (10 of 36 dogs; 28%), gastrointestinal adverse effects (9 of 36 dogs; 25%), sepsis (2 of 36 dogs; 5%), and hemorrhagic cystitis (1 of 36 dogs; 3%). There were no deaths related to the treatment. One dog developed lymphoma after the fourth cycle of chemotherapy and had no evidence of HSA at the time of death. 4 JAAHA 49:6 Nov/Dec 2013

5 VAC for Dogs with Stage III Hemangiosarcoma FIGURE 4 A: A left lateral radiographic image from a dog with stage III splenic HSA with evidence of diffuse lung metastases. B: A left lateral radiographic image from the same patient as in Figure 4A that achieved a complete response (CR) after two cycles of a VAC chemotherapy protocol. Discussion The age, gender, and breed distribution of the affected dogs in this study were similar to those previously reported in dogs with HSA. 1,2,4,17 The prevalence of clinically detectable metastases at the time of initial diagnosis was 41% (73 of 179 dogs); however, some dogs were not completely staged. Therefore, the prevalence of metastases may have been underestimated. That metastatic rate was similar to the metastatic rate previously reported for dogs with splenic HSA 1 3,16,17,22 All dogs included in this study were treated with the multiagent VAC protocol. Previous studies have evaluated single- and multiagent adjuvant chemotherapy protocols for HSA; however, those different protocols have never been directly compared FIGURE 5 A: Transverse view of an MRI from a dog with a muscular HSA located in the right ipsoas muscle. The tumor is indicated by arrows. B: An MRI from the same patient as in Figure 5A that achieved a CR after three cycles of a VAC chemotherapy protocol. The previous location of the tumor is indicated by arrows. L, left, R, right. prospectively. Thus, whether multiagent doxorubicin-based protocols have greater efficacy than single-agent doxorubicin protocols remains unresolved. In a previous study using doxorubicin as a single agent, the MST in dogs of all stages was not published, and only dogs with stage I and complete excision were included to estimate a MST of 172 days. 15 Therefore, comparison of the JAAHA.ORG 5

6 MST of the current study with the MST of other multiagent doxorubicin-based protocols (where different stages were included) is not possible. Another study evaluating dogs with splenic HSA treated with surgery, immunotherapy, and adjuvant chemotherapy using a protocol containing vincristine, cyclophosphamide, and methotrexate had a MST of 117 days, suggesting that drugs other than doxorubicin (e.g., vincristine and cyclophosphamide) may have some effect in the treatment of dogs with HSA. 2 Based on this rationality, together with previous clinical observations by the authors of the efficacy of the VAC protocol, the VAC protocol has become the standard chemotherapeutic approach for dogs with HSA at the authors institution and was the protocol chosen for this study. In this study, the authors found no statistically significant difference in the MST for dogs with gross evidence of metastasis at initial diagnosis and dogs without evidence of metastasis, suggesting that the presence of gross metastatic disease should not be a significant factor in clinical decision making for using the VAC protocol. That finding is similar to a previous study where 10 dogs with stage III HSA in different anatomic location received a similar VAC protocol. 1 The MST for those patients was 172 days, and no difference was found when compared with other clinical stages. 1 The 1 yr response rates in the current study for stage I/II and III were 14% and 4%, respectively. For splenic HSA, the 1 yr survival rates were 12% and 8% for stage I/II and III, respectively. The 1 yr survival rates and MSTs of the dogs in the current study were similar to those reported previously with dogs with splenic HSA treated with postoperative doxorubicin-based protocols. 1,3,14 17 Previously published MSTs of 87 days (doxorubicin and cyclophosphamide protocol), 107 days (dose-intensified doxorubicin protocol), and 136 days (doxorubicin and cyclophosphamide/minocycline protocol) have been reported. 3,16,17 Although the MST for the dogs with stage III HSA in the current study appeared to be longer than those previously reported in dogs with similar stage treated with other doxorubicin-based protocols, documenting that difference would require prospective studies comparing different protocols. Interestingly, the MST and 1yr survival proportion for dogs with stage I/II did not appear different to those in previously published studies. 1,3,15 17 The MST for dogs with subcutaneous HSA in the current study appeared shorter than in a previous study with dogs with subcutaneous HSA; however, in that study, none of the dogs had evidence of metastasis. 12 In the current study, 30% of dogs had evidence of distant metastases; however, the MST in the current study for dogs with subcutaneous HSA without evidence of distant metastasis appeared to be shorter than in the previous study (MST of 210 days in the current study versus 1,553 days from the previously reported study). 12 That difference likely was areflection of the small number of dogs in both studies (12 dogs in the current study versus 17 dogs in the previously reported study). In another study of dogs with subcutaneous HSA and measurable disease, the overall response rate to chemotherapy using doxorubicin-based protocol was 39%. 18 Although only three dogs in that study received a protocol containing doxorubicin, cyclophosphamide and vincristine, the protocol was not explained in detail. One of those three dogs achieved a PR for a total duration of 190 days, whereas the other two dogs achieved SD. The overall response rate seen in the current study appeared higher than in that previous study. Both studies demonstrated that dogs with measurable disease may respond to doxorubicin based protocols such as the VAC protocol. 18 In a recent study, dogs with subcutaneous HSAs (without muscular involvement) treated with doxorubicin-based protocols had a MST of 212 days. 14 That MST was similar to the MST found in the current study (210 days). In that study, evidence of metastasis at the time of diagnosis was a negative factor for survival; however, those results were difficult to compare because dogs were treated with different doxorubicinbased protocols, surgery, and/or radiation therapy. 14 The high response rate in the current study needs to be interpreted with caution because the response was evaluated only in dogs who had follow-up measurement re-evaluation (e.g., radiographs, abdominal ultrasonography, etc.) and who had a recorded response (28 of 67 dogs); therefore, a total of 39 dogs did not have follow-up measurement re-evaluation, and the response rate in those dogs was unknown. It is likely that some of those dogs were not re-evaluated due to progressive clinical signs for possible PD, thus potentially biasing these study results. Another factor that may have contributed to a possible overestimation of the response rate was that in some dogs, the VAC protocol was started; however, due to progressive clinical signs the first cycle was not completed. Those dogs were not included in the study and likely had PD. If those dogs were included in the evaluation of response rate, the CR, PR and SD rates would be lower and the PD rate would be higher. Finally, the response rate could have been overestimated because it was typical for those tumors to present with secondary large blood clots (i.e., either intra- or peritumoral bleed) or cavitated lesions, which could change the size and shape of the tumor over time. The findings in the current study do not suggest a clear advantage for using the VAC protocol over other doxorubicin-based protocols for dogs in stage I and II HSAs; however, the high response rate and prolonged MST in dogs with stage III HSA in this study suggested a possible advantage for using it in dogs with advanced clinical stage. The reason why dogs with liver metastasis had shorter MSTs than dogs with pulmonary metastasis was unknown. One possibility is that because pulmonary metastatic lesions in dogs 6 JAAHA 49:6 Nov/Dec 2013

7 VAC for Dogs with Stage III Hemangiosarcoma with HSA tended to be smaller in size (i.e., miliary) and they might have been more responsive than the larger cavitated lesions that tended to appear in the liver (i.e., smaller masses had higher growth fraction and mitotic indices, and a shorted doubling time than larger lesions). Also, it was possible that liver metastases were more likely to have clinically relevant bleeds than lung metastases, thus contributing to increased morbidity and mortality. Although other reasons could not be excluded, it was also possible that the difference in survival was reflected by a small number of dogs evaluated in each category. That finding should be evaluated in a prospective manner using a large number of dogs. One limitation of this study was that, in most patients, the metastatic lesions were not evaluated either cytologically or histopathologically. The presence or absence of metastases was determined primarily by clinical and imaging findings; therefore, it was possible that some of the lesions were either not related to the tumor or were benign lesions, such as hematomas or regenerative nodules, intrapulmonary hemorrhage, or other neoplastic or nonneoplastic lesions. Another limitation of this study was that, in most dogs, clinical staging was performed using traditional imaging procedures such as radiography and abdominal ultrasonography; therefore, it was likely that if more advance image modalities, such as either computer tomography or MRI were used, some dogs with stage I/II could have been more accurately staged and classified as stage III. However, based on the results of this study, detecting a potential metastatic lesion should not be a reason for denying treatment of dogs with HSA. In this study, the WHO system was used for evaluation of response. The WHO system for humans was modified to be used in domestic animal tumors and is one of the most commonly known criteria for evaluating response for solid tumors in human and veterinary medicine. 19 Other systems had been established, such as the Response Evaluation Criteria in Solid Tumors criteria. 23,24 In human and veterinary studies, similar results had been found when both systems were compared. 18,23 25 It is unlikely that the overall response rate will differ if the Response Evaluation Criteria in Solid Tumors criteria had instead been used in the current study. Another limitation of this study was that the authors did not include a group of patients treated with surgery alone. Based on the authors previous collective experience, the Ohio State University Veterinary Medical Center almost never recommends surgery alone for dogs with HSA. Owners are counseled to consider chemotherapy as part of the treatment of their dogs before the patient undergoes surgery. Therefore, the number of dogs with HSA treated with surgery alone would have been too small for statistical comparison. No lethal toxicities were observed in this study; however, being a retrospective study, it was difficult to determine the prevalence and severity of toxicity because the information obtained was dependent on what was reported in the medical records. Therefore, it is possible that the toxicity was underestimated. Treatment delay and/or dose reductions were recorded in 53% of the patients associated with at least one of the treatments; however, the protocol in general was well tolerated and the prevalence of toxicity and sepsis appeared to be similar to other doxorubicin-containing protocols previously reported. 1,3,16,17,26 Because of the expected myelosuppressive effects of the drug combination and the consequent expectedincreasednumber of neutropenic episodes, an oral prophylactic antibiotic (trimethoprim/sulfamethoxazole) was integrated into the protocol. There is still controversy about the benefit of administering prophylactic antibiotics to patients receiving chemotherapy. 27 In a review study of the use of prophylactic antibiotic therapy in human cancer patients, the use of either oral prophylactic quinolones or trimethoprim/sulfamethoxazole in neutropenic oncologic patients was effective in decreasing gram-negative bacteremia and, therefore, infection-related mortality. 27 In the veterinary literature, the use of oral prophylactic trimethoprim/ sulfamethoxazole was found to be beneficial in reducing morbidity in dogs with either osteosarcoma or lymphoma during the first 14 days after treatment with doxorubicin. 28 It is possible that the use of prophylactic trimethoprim/sulfamethoxazole in the protocol used in this study helped to reduce the adverse effects related to neutropenia. The prevalence of sterile hemorrhagic cystitis in the current study was consistent with previous studies using protocols containing cyclophosphamide. 29 In the VAC protocol used in this study, cyclophosphamide was given at a dosage of mg/m 2 PO on day 10 (Table 2); thus, it differed from the VAC protocol previously reported in which the cyclophosphamide was given IV on day 1. 1 When compared with the previous VAC protocol, the prevalence of neutropenia was lower in the current study (28% versus 73%), and there was no mortality due to sepsis; however, the prevalence of gastrointestinal toxicity was similar (25% versus 33%). 1 The authors version of the VAC protocol appeared to be better tolerated; however, because of the retrospective nature of the current study, the toxicity could be underestimated. Finally, the relatively low number of cases evaluated in this study might have represented a statistical error. Being a retrospective study there was no standard evaluation for response, which could have affected the results. A prospective study of dogs with HSA with stage I/II and III warrants further investigation. Conclusion The authors found that dogs with stage III HSA treated with a VAC protocol had a similar prognosis as dogs with stage I/II HSA. JAAHA.ORG 7

8 Subcutaneous HSA was aggressive in dogs, similar to the aggressiveness of splenic HSA. Finally, the authors version of the VAC protocol was well tolerated with no mortality due to adverse events. Therefore, the authors believe that dogs with HSA and evidence of metastases at the time of diagnosis should not be denied treatment. FOOTNOTES a GraphPad Prism 4.0; GraphPad Software Inc., San Diego, CA REFERENCES 1. Hammer AS, Couto CG, Filppi J, et al. Efficacy and toxicity of VAC chemotherapy (vincristine, doxorubicin, and cyclophosphamide) in dogs with hemangiosarcoma. J Vet Intern Med 1991;5(3): Brown NO, Patnaik AK, MacEwen EG. Canine hemangiosarcoma: retrospective analysis of 104 cases. J Am Vet Med Assoc 1985;186(1): Sorenmo KU, Jeglum KA, Helfand SC. Chemotherapy of canine hemangiosarcoma with doxorubicin and cyclophosphamide. J Vet Intern Med 1993;7(6): Clifford CA, Mackin AJ, Henry CJ. Treatment of canine hemangiosarcoma: 2000 and beyond. 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