Evaluation of strontium Sr 90 for the treatment of superficial squamous cell carcinoma of the nasal planum in cats: 49 cases (1990-2006)

Objective-To determine progression-free and overall survival times of cats with squamous cell carcinoma (SCC) of the nasal planum following treatment with a single fraction of strontium Sr 90 (Sr-90). Design-Retrospective case series. Animals-49 cats with SCC of the nasal planum. Procedures-Information including FIV infection status, diagnosis of SCC vs SCC in situ (ie, evidence that the tumor did or did not penetrate the epidermal basement membrane, respectively), Sr-90 dose and number of probe applications, treatment-related response and complications, and recurrence of SCC and new lesion development was obtained from medical records. The relationships of these variables with calculated progression-free and overall survival times were assessed. Results-Of 49 cats that underwent Sr-90 plesiotherapy (median dose, 128 Gy), 48 (98%) had a response to treatment and 43 (88%) had a complete response. Median progression-free and overall survival times were 1,710 and 3,076 days, respectively. Treatment complications were infrequent (4 [8%] cats) and mild. Following treatment, the SCC recurrence rate was 20% (10/49 cats); 16 (33%) cats developed new lesions in other locations. Overall survival time was significantly longer for cats with a complete response to treatment than for those with a partial response. None of the other variables evaluated had a significant effect on progression-free or overall survival time. Conclusions and Clinical Relevance-Treatment of cats with SCC of the nasal planum with a single fraction of Sr-90 appeared to be effective and well tolerated. Initial response to treatment was predictive of overall survival time.