A preliminary assessment of whole-body radiotherapy interposed within a chemotherapy protocol for canine lymphoma

Six dogs with spontaneously occurring, previously untreated lymphoma were treated with half-body radiation therapy (RT) doses interposed in a CHOP-based 25-week chemotherapy regimen. Chemotherapy-related toxicities were as expected and were mildly increased in severity post-RT compared with pre-RT. Treatment was delayed by 1-2 weeks per delay in four dogs due to chemotherapy-related neutropenia. Radiation therapy was administered in two consecutive day fractions of 4 Gray to the cranial and caudal halves of the body 4 weeks apart. Radiation-related toxicities consisted of lethargy, alopecia, diarrhoea of less than 2-day duration and average decreases in neutrophil counts of 50%. Late effects from RT were not evident. Median remission and survival times for the six dogs were 455 and 560 days, respectively. The protocol was well tolerated and should be studied further to evaluate the potential therapeutic gain of the addition of RT to chemotherapy for the treatment of canine lymphoma.