Long-term outcome associated with intratumoral chemotherapy with cisplatin for cutaneous tumors in equidae: 573 Cases (1995-2004)

Objective - To determine outcome associated with cutaneous tumors treated via intratumoral chemotherapy with cisplatin and identify risk factors affecting local tumor control and complications in equidae. Design - Retrospective case series. Animals - 573 equidae with 630 cutaneous tumors. Procedures - Medical records of horses, mules, donkeys, and ponies with cutaneous tumors treated via intratumoral chemotherapy with cisplatin were analyzed. Results - 549 horses, 13 mules, 8 donkeys, and 3 ponies with 630 histologically confirmed cutaneous tumors were included. Tumors included sarcoids (n = 409), squamous cell carcinomas (151), soft tissue sarcomas (28), cutaneous lymphomas (26), and melanomas (16). Overall cure rate, defined as local control at 4 years, was 93.3%. For all tumor stages combined, cure rates after 1 course of treatment were 96.3% for sarcoids, 96% for lymphomas, 88% for squamous cell carcinomas, 85% for soft tissue sarcomas, and 81% for melanomas. Treatment protocol, tumor stage, and prior treatment were significant prognostic factors for tumor control. Treatment efficacy was lower for large tumors, those with gross postoperative residual disease, and those that had been treated previously with other modalities. Treatment was well tolerated. Local reactions were more likely to occur and to be more severe after the third and fourth treatment sessions. Conclusions and Clinical Relevance - Results confirmed the value of intratumoral chemotherapy with cisplatin for treatment of cutaneous tumors in equidae. The results cannot be extrapolated to other formulations of cisplatin or other protocols that might be used.