A retrospective analysis of radiation therapy for the treament of feline vaccine-associated sarcoma

Abstract

We retrospectively evaluated predictive prognostic factors in 73 cats with vaccine-associated sarcoma given postsurgical curative (n=46, most with clean margins) or coarse fractionated radiotherapy (n=27, most with either macroscopic disease or dirty margins). The former animals displayed a median survival of 43 months and a median progression free interval (PFI) of 37 months, the latter reached a median survival of 24 months and a median PFI of 10 months. In cats undergoing coarse fractionated therapy, factors predictive of a better outcome included lack of visible mass (n=10) as opposed to macroscopic disease (n=17, survival: 30 vs. 7 months, P=0.025; PFI: 20 vs. 4 months, P=0.01), adjuvant chemotherapy for gross disease (n=5/17, survival: 29 vs. 5 months, P=0.04) and a smaller number of surgeries preceding radiation therapy (Coeff=0.41, P=0.03). The Ki67-index was not predictive for survival. We concluded that postsurgical curative and coarse fractionated radiotherapy are both effective legitimate options for managing vaccine-associated sarcomas.