Radiation therapy for persistent or progressive mediastinal lymphoma after chemotherapy in FeLV ‐positive cats: a retrospective case series of four cats

BACKGROUND: Mediastinal lymphoma in feline leukaemia virus (FeLV)-positive cats is associated with a poor prognosis, and therapeutic options may be limited when adequate disease control is not achieved with chemotherapy. The efficacy of radiation therapy in this setting has not been established. CASE REPORT: Medical records were retrospectively reviewed for FeLV-positive cats diagnosed with mediastinal lymphoma between November 2018 and December 2024 that had persistent or progressive mediastinal disease after chemotherapy and were subsequently treated with radiation therapy. Treatment response was assessed by computed tomography using the Response Evaluation Criteria in Solid Tumours (RECIST). Three of four cats (75%) responded to radiation therapy (two complete responses, one partial response). Respiratory signs improved rapidly in three cats (median 5 days). Local disease control was achieved in most cases; however, three cats developed progression at other sites. Survival times were 45, 150 and 352 days in cats that died, and one cat remained alive for >626 days at the time of last follow-up. No severe radiation-related adverse effects were documented during the available follow-up, although systematic evaluation of late radiation toxicity was not possible. CONCLUSION: Radiation therapy may provide local control and rapid palliation of respiratory signs in FeLV-positive cats with persistent or progressive mediastinal lymphoma after chemotherapy. Further studies with larger cohorts are warranted.