Introduction

Hypofractionated radiation therapy (RT) and bisphosphonates are commonly utilized for palliative intent treatment of canine osteosarcoma (OSA). Consensus has not been reached as to whether these treatments should be administered concurrently. The primary objective of this study was to evaluate outcome in dogs treated with hypofractionated RT, with and without the addition of bisphosphonates. A secondary objective was to identify prognostic factors in this population.

Methods

Dogs with presumed and confirmed OSA of the appendicular limb treated with daily hypofractionated RT (8 Gy x 2 fractions) at the Flint Animal Cancer Center between 2010 and 2019 were evaluated retrospectively. Clinical data were abstracted from the medical records, and adjuvant therapies were noted. Outcome was assessed using medical records and electronic follow up.

Results

There were 165 dogs included. Sixty-eight dogs received bisphosphonates as part of their palliative intent treatment. Median survival time from the first RT treatment to death was not significantly different between groups (p=0.758). Only age (>/=9 years) was found to be prognostic in this population (p=0.031). Factors not associated with survival time included bisphosphonate drug type, timing of bisphosphonate administration, tumor location, weight, breed, sex, time from diagnosis to treatment, concurrent administration of chemotherapy, and amputation.

Conclusion

This study suggests no difference in outcome for dogs treated with and without bisphosphonates in addition to hypofractionated RT. Prospective studies are needed to determine if the addition of bisphosphonates to hypofractionated RT leads to an improved quality of life in dogs undergoing palliative intent treatment for OSA.