Veterinary Medicine - February 2009 - (Page 80) Canine anal sac adenocarcinoma In one study, two of four dogs with unresectable anal sac gland carcinomas that received carboplatin exhibited decreased mass size suf cient to permit surgical resection.6 In the same study, 12 of 40 dogs with iliac lymphadenopathy had relief of fecal obstipation after carboplatin treatment.6 A different study reported a partial reduction in tumor size in four out of 13 dogs with anal sac adenocarcinoma treated with cisplatin alone and in one out of three dogs treated with carboplatin alone.4 Favorable survival times have been reported in dogs treated with radiation, surgery, and mitoxantrone (n = 15) and surgery with oral daily melphalan (n = 19); however, the individual role of chemotherapy in those studies cannot be determined as there were no control groups.5,7 Given the reported partial responses, the platinum agents appear to have some ef cacy against anal sac adenocarcinoma and may be appropriate for adjuvant or neoadjuvant (preliminary) therapy. PROGNOSIS The survival time for dogs with anal sac adenocarcinoma varies, and retrospective studies have attempted to identify signi cant prognostic factors. The overall median survival time in two larger studies evaluating 80 and 113 dogs was 479 and 544 days, respectively.6,8 The dogs in these studies received a wide variation in treatments, including surgery, radiation therapy, and chemotherapy, making it dif cult to draw conclusions about the effect of individual treatment modalities or effective chemotherapy protocols. In the larger study, dogs that underwent surgery as a part of their treatment had an improved survival time compared with dogs that received chemotherapy alone.8 Larger tumors, the presence of distant metastatic disease, and hypercalcemia have been variably associated with a signi cantly decreased survival time.3,6,8 The median survival time was higher at 956 days 80 VETERINARY MEDICINE
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