Adjuvant chemotherapy with mitoxantrone for cats with mammary carcinomas treated with radical mastectomy

The purpose of this study was to investigate the disease-free interval, survival time and adverse events of a combined treatment approach in cats with mammary malignant tumors using radical mastectomy and adjuvant mitoxantrone.

All cats underwent surgery to remove the mammary chain containing the tumors. A 3 cm margin was obtained around removed tumors. For staging purposes, regional inguinal lymphadenectomy was performed in all cases. After histopathology, cats were staged according to the World Health Organization's (WHO) staging system. Chemotherapy with mitoxantrone was started 15-30 days after surgery (6 mg/m(2) IV every 21 days for four cycles) with the objective of delaying metastasis.

Three cats were intact, one cat was early spayed, four cats were late spayed and four cats were spayed at an unknown age. Based on the WHO's staging system, six cats were classified as stage I and six cats as stage III. The median disease-free interval and survival time were 360 and 480 days, respectively. Four (33%) cats received four doses of mitoxantrone, four (33%) cats received three doses and four (33%) cats received only one dose. The most frequent adverse effects of chemotherapy were azotemia, anorexia, leukopenia and vomiting.

Adjuvant mitoxantrone chemotherapy may be an option for feline mammary tumors. Further, sufficiently powered, randomized prospective trials are necessary to determine if mitoxantrone is superior, inferior or equivalent to doxorubicin in the adjuvant setting.