Cancer-induced bone
pain, despite its frequency and severity, is a poorly understood phenomenon in people and animals. Despite excitement regarding translational
osteosarcoma studies, there is a lack of attention toward examining
cancer pain in dogs. In this pilot study, we used a multimodal
pain assessment methodology to evaluate
pain relief after therapeutic intervention in dogs with primary
bone cancer. We hypothesized that intervention would cause objective evidence of
pain relief. Evaluations of 8 dogs with primary
bone cancer included
18F-FDG PET/CT scans, kinetic analysis, validated owner questionnaires (Canine Brief
Pain Inventory, canine BPI), and serum
N-telopeptide (NTx) concentration. Dogs were routinely staged and had
18F-FDG PET/CT scans prior to treatment with day 0, 7, 14, and 28 canine BPI, serum NTx, orthopedic exam, and kinetic analysis. Dogs treated with
zoledronate and radiation underwent day 28
18F-FDG PET scans. All clinical trial work was approved by the University of Missouri IACUC. Four dogs underwent
amputation (
AMP) for their appendicular bone
tumors; four received neoadjuvant
zoledronate and hypofractionated
radiation therapy (ZOL+RT). Canine BPI revealed significant improvements in
pain severity and
pain interference scores compared to baseline for all dogs. Positive changes in peak vertical force (+16.7%) and vertical impulse (+29.1%) were noted at day 28 in ZOL+RT dogs. Dogs receiving ZOL+RT had a significant (at least 30%) reduction in serum NTx from baseline compared to amputated dogs (p = 0.029). SUVmax (p = 0.11) and intensity (p = 0.013) values from PET scans decreased while
tumor uniformity (p = 0.017) significantly increased in ZOL+RT-treated
tumors; gross
tumor volume did not change (p = 0.78). Owner questionnaires, kinetic analysis, and
18F-FDG PET/CT scans showed improved
pain relief in dogs receiving ZOL+RT. Serum NTx levels likely do not directly measure
pain, but rather the degree of systemic osteoclastic activity. Larger, prospective studies are warranted to identify the ideal objective
indicator of
pain relief; however, use of multiple assessors is presumably best. With improved assessment of
pain severity and relief in dogs with
cancer, we can better evaluate the efficacy of our interventions. This could directly benefit people with
cancer pain, potentially decreasing the amount of subtherapeutic novel drugs entering human clinical trials.