Use of surgery and electron beam irradiation, with or without chemotherapy, for treatment of vaccine-associated sarcomas in cats: 78 cases (1996-2000).

To evaluate responses of cats with vaccine-associated sarcomas to treatment with surgery and radiotherapy, with or without adjunctive chemotherapy. Retrospective study. 76 cats (78 tumors). Medical records were reviewed. Factors potentially associated with survival time, time to recurrence, and time to development of metastases were evaluated. Following excision, electron beam radiation, and, in some cases, chemotherapy, 32 (41%) cats experienced recurrence, and 9 (12%) cats developed metastases. One- and 2-year survival rates were 86 and 44%, respectively. Median survival time from onset of disease was 730 days (range, 30 to 2,014 days). Median disease-free interval was 405 days (range, 30 to 925 days). Cats that underwent only 1 surgery prior to radiotherapy had a lower recurrence rate than did cats that underwent > 1 surgery and had a significantly longer disease-free interval. Survival time and disease-free interval decreased as time between surgery and the start of radiotherapy increased. Cats that developed metastases had significantly shorter survival times and disease-free intervals than did cats that did not develop metastases. Castrated male cats had a significantly shorter survival time than did spayed female cats. Cats with larger tumors prior to the first surgery had shorter survival times. Twenty-six cats received chemotherapy in addition to surgery and radiotherapy. Whether cats received chemotherapy was not associated with recurrence rate, metastasis rate, or survival time. Results suggest that excision followed by electron beam irradiation may be beneficial for treatment of cats with vaccine-associated sarcomas. Extent of excision prior to radiotherapy did not seem to be associated with recurrence rate.