INTRALESIONAL IMPLANT FOR TREATMENT OF PRIMARY ORAL MALIGNANT-MELANOMA IN DOGS

The feasibility, safety, and efficacy of a new method of local, sustai ned-release chemotherapy by use of intralesional cisplatin implants we re evaluated in the treatment of oral malignant melanoma. The implant is an injectable viscous gel composed of a protein carrier matrix, a v asoactive modifier, and a chemotherapeutic drug. Twenty dogs with biop sy-proven melanomas were treated at 1- to 2-week intervals by injectio n with cisplatin implant. Tumors weve treated until they resolved or w ere judged to be unresponsive. In 3 dogs with tumors unresponsive to c isplatin implants, methotrexate implants were used, and in 2 of these dogs, carmustine implants followed the methotrexate. Tumor responses w ere evaluated by sequential measurements. Melanomas in 14 (70%) of 20 dogs had a > 50% decrease in volume, and in 11 (55%) of these dogs, ha d a complete response. Tumors with complete responses received a mean cisplatin dose of 11.7 +/- 1.8 mg, delivered in a mean of 2.6 treatmen ts. Two of the dogs with complete response also were treated with meth otrexate and carmustine. Implants were well tolerated. Local necrosis, limited to the treatment site, developed in most tumors (17/20) and w as associated with tumor response. Systemic toxicosis was minimal; ren al insufficiency after cisplatin implants was not evident. Median surv ival times of dogs with complete tumor response (51 weeks) wets substa ntially greater than that of dogs without local tumor control (10.5 we eks). Recursive partitioning analysis of variables indicated that mand ibular tumors of short duration were associated with a positive outcom e. Multivariate linear regression analysis revealed the benefit of a g reater number of cisplatin implants in a consistent weekly treatment c ourse. The success of the intralesional chemotherapy indicated that im plants ave a technically feasible modality for local control of or-al melanomas in dogs and provide possible alternative treatment to radiat ion therapy or surgery.