Treatment of feline gastrointestinal intermediate- or large-cell lymphoma with lomustine chemotherapy and 8 Gy abdominal cavity radiation therapy

Abstract

Objectives The goal of this study was to document the outcomes and toxicity of a novel multimodality treatment protocol for feline gastrointestinal intermediate- or large-cell lymphoma (FGL) in which cats were treated at 21-day intervals. Methods This was a prospective, single-arm study. Twelve client-owned cats with cytologically diagnosed FGL were treated with a combination of abdominal cavity radiation therapy (RT; 8 Gy total dose administered in two 4 Gy fractions, 21 days apart), lomustine chemotherapy (approximately 40 mg/m2, administered orally at 21-day intervals for four treatments), prednisolone (5 mg PO q24h) and cobalamin (250 µg/week SC). Results Three cats were euthanized prior to the second treatment and it was difficult to discern treatment-associated toxicity from progressive disease. Four of the remaining cats developed cytopenias, resulting in 7–14-day lomustine treatment delays and/or dose reductions. Six cats had a partial response to treatment and three had stable disease based on ultrasound at day 21 (50% overall response rate). Three of these six cats completed the study and lived >240 days; one died of refractory diabetes mellitus with no clinical evidence of FGL, and the other two died as a result of FGL. The median overall survival time was 101 days (95% confidence interval [CI] 9–240). The median progression-free survival time was 77 days (95% CI 8–212). Necropsies were performed in eight cats, which revealed multifocal lymphoma throughout the gastrointestinal tract and other organs. Conclusions and relevance Oncological outcomes reported herein are comparable to those achieved with multiagent injectable chemotherapy (eg, CHOP). Treatment was seemingly well tolerated in most cats and was relatively cost-effective. It is therefore plausible that improved disease control may be achievable through continued optimization and intensification of the combinatorial chemoradiotherapy protocol.