Evaluation of thalidomide in the treatment of canine malignant mammary gland neoplasms

The neoplasms of the canine mammary gland are the most common neoplasm in intact female dogs, and at least 50% are malignant. Most invasive carcinomas present a survival lower than two years when treated solely with surgery, which consists in the main treatment approach for the disease. Thalidomide has demonstrated clinical benefit in several neoplastic and non-neoplastic diseases, mainly due to its antiangiogenic and immunomodulatory properties. Therefore, the aim of the present study was to evaluate the therapeutic effects of thalidomide in female dogs diagnosed with malignant neoplasms of the mammary gland. Initially, the adverse events of the thalidomide treatment were evaluated in 29 female dogs treated with 20 and 10 mg/kg/day during 6 months. The drug was well tolerated, not interfering with the activities of daily living of most of the studied population. In cases where excessive somnolence was present the 10 mg/kg/day should be indicated. Afterwards, 58 female dogs were divided into four different treatment proposals: surgical treatment, surgery followed by maximum tolerated dose chemotherapy (MTDC), surgery, MTDC, and thalidomide, and surgery, MTDC, and metronomic chemotherapy (MC). No statistically significant difference in overall survival (OS) was observed between the four proposed treatments when animals presenting all clinical stages were evaluated (p=0.3177). However, the analysis of OS of animals presenting distant metastasis, the surgery, MTDC associated to thalidomide and MC presented a longer OS, 463 and 376.5 days, respectively, when compared to the surgical and surgery plus MTDC protocols, 150 and 148 days, respectively. Furthermore, we report the case of a female dog diagnosed with a carcinosarcoma that presented a 20-month OS following the diagnosis of pulmonary metastasis solely treated with thalidomide. The treatment with surgery, MTDC and thalidomide was considered effective and safe in canine patients with advanced stage mammary gland neoplasms, increasing the OS of patients diagnosed with distant metastasis. MC may be associated to surgery and chemotherapy when thalidomide is not available. (AU)