Postsurgical intra-incisional 5-fluorouracil in dogs with incompletely resected, extremity malignant spindle cell tumours: a pilot study

The safety and efficacy of intra-incisional 5-fluorouracil (5-FU) in the management of incompletely resected malignant spindle cell tumours of extremities was evaluated in six dogs. After marginal surgery, the dogs underwent weekly intra-incisional 5-FU for a minimum of six cycles. Treatment was well tolerated by all dogs, with no systemic adverse effects and only one episode of local cutaneous hyperpigmentation, which completely and spontaneously resolved. Median follow-up for all the dogs was 546 days (mean 619; range 297-1207). At the date of analysis, four dogs were still alive with no evidence of local recurrence, and two dogs had died as a result of their disease. The cause of death was development of distant metastases in one dog and tumour regrowth in the other. Despite the small sample size, this study documents that intra-incisional 5-FU chemotherapy is a safe and efficacious adjuvant treatment in the case of incompletely resected malignant spindle cell tumours in dogs and that long disease control can be achieved.