Long‐term complete remission following low‐dose (20 Gy) radiation therapy for extensive metastatic seminoma in a dog

Summary A 10‐year‐old, cryptorchid Lhasa Apso diagnosed with a metastatic seminoma was referred for radiation therapy following non‐durable response to multiple chemotherapies. The tumour was multifocal, metastatic and extensive, invading the vena cava and engulfing the aorta. The patient was deemed to be a poor surgical candidate, and radiation therapy (20 Gy in 10 daily fractions) was administered. The patient remained in complete remission for 1028 days from diagnosis and 880 days from the first radiation therapy treatment. Only Grade 1 Veterinary Radiation Therapy Oncology Group perineal skin toxicity was reported as an acute side effect, with no late toxicity. This report concludes that extensive metastatic seminomas can be successfully treated with low‐dose radiation therapy.