COMPARISON OF INTRATUMORAL ADMINISTRATION OF CISPLATIN VERSUS BLEOMYCIN FOR TREATMENT OF PERIOCULAR SQUAMOUS-CELL CARCINOMAS IN HORSES

Objective-To compare therapeutic benefits of intratumoral administrati on of cisplatin and bleomycin for squamous cell carcinoma of the eyeli ds in horses. Animals-25 horses with 27 T2-stage periocular squamous c ell carcinomas. Procedure-Horses were treated 4 times at 2-week interv als with a slow-release formulation of cisplatin (1 mg/cm(3) of tissue ) or bleomycin (1 IU/cm(3) of tissue). A two-stage design was used to minimize the sample size in each treatment arm. Results-The local cont rol rate at 1 year for lesions treated with cisplatin was 93 +/- 6%, a nd with bleomycin was 78 +/- 10%. Difference in local control duration between the 2 treatment groups was not significantly different. A hig h tumor proliferative fraction index value was associated with a highe r local (infield) control rate, but also with a higher risk of margina l and regional recurrences. Tumors with a low proliferative fraction i ndex value (< 28%) had 9.5-times higher (P = 0.0411) risk df recurrenc e than those with a high index value. Local acute reactions were simil ar in the 2 treatment groups, and chronic reactions were not observed. Conclusions-Cisplatin and bleomycin were effective anticancer agents for carcinoma of the eyelid in horses. Based on therapeutic benefit an d treatment cost, cisplatin was found to be a better choice for intrat umoral chemotherapy of eyelid carcinomas. Clinical Relevance-Results o f this study confirm the value of intratumoral chemotherapy, using cis platin, for treatment of cutaneous squamous cell carcinomas in horses.