Cisplatin (cisplatinum or cis-diamminedichloroplatinum(i)) is a platinum-based chemotherapy drug used to treat various types of skin cancers of horses, including melanomas, sarcoma, carcinoma, lymphomas, and germ cell tumors. It was the first member of its class, which now also includes carboplatin and oxaliplatin.

Though cisplatin has shown efficacy against a number of tumors in small studies, the size of the studies, the many varied ways of preparing the cisplatin, dosages, and a myriad of other problems makes evaluation difficult. In 2007 a very large study that standardizes preparation and administration. Using much of the recent research to maximize effectiveness and minimize reactions the results are a surprisingly successful long term results against the most common yet sometimes difficult to treat tumors of horses.

But there are 2 flies in the ointment here. The first is the particular formulation used here (Matrix Pharmaceuticals a division of Novartis) is not readily available and as near as I can research, it is still in the approval process with the FDA and would be difficult to formulate. The second fly is the safe handling of cisplatin requires education. That said I would hope the tremendous results here spur development of this product and in tough tumor cases might well be worth pursuing.

Cisplatin is one of the most effective anticancer agents used in the treatment of solid tumors in humans. However, its use as systemic agent has been limited by its toxicity, as well as by the occurrence of resistance. Several approaches have been developed to decrease its toxicity without impairing its therapeutic activity. Intratumoral administration of cisplatin exploits dose-response effects by maximizing drug concentrations in localized tumors while minimizing exposure of normal tissue. Cisplatin is an ideal drug for intratumoral chemotherapy because it does not cause tissue necrosis and its effects are dose and time dependent. The therapeutic index of intratumoral administration of cisplatin may be optimized by increasing drug exposure via slow-release drug carrier like biological oils in combination with vasoconstrictors.

Intratumoral chemotherapy with cisplatin formulated in a viscous fluid formulation is practical and effective for treatment of a wide variety of equine cutaneous tumors. Most reports of intratumoral chemotherapy with cisplatin in horses have included only a limited number of cases. The purpose of the study reported here was to evaluate the therapeutic value of intratumoral chemotherapy with cisplatin in sesame oil emulsion in a large series of equidae with various common skin tumors and determine prognostic factors associated with response to treatment and toxicosis.