Correlations between acute radiation scores and pain scores in canine radiation patients with cancer of the forelimb

Objective To determine whether there is a correlation between skin acute radiation score (ARS) and pain scores and to determine if skin ARSs can be used to predict future pain scores and increased need for analgesia in dogs undergoing radiation therapy for cancer of the forelimb. Study design Prospective observational study. Animals Seven middle‐aged dogs of various breeds with cancer of the forelimb. Methods Each neoplasm was surgically removed and a histologic diagnosis was obtained. Curative intent radiation therapy was initiated 2½–4½ weeks after surgery. Curative intent radiation therapy was delivered as prescribed. Two trained observers scored the dogs using a visual analog pain scale (VAS), Glasgow composite measure of pain scale, short form (GCMPS) and skin ARS prior to each day’s therapy. Daily scores were averaged and scatter plots were developed. Generalized estimating equation regressions were used to calculate standard error, 95% confidence interval, and p‐values for each relationship. Confidence and prediction bands were plotted. Results A statistically significant correlation between skin ARS and VAS and GCMPS pain scores was identified indicating that as the skin ARS increased so did the pain scores. A general correlation between VAS and GCMPS scores was observed. Early (fraction days 1–6) GCMPS scores were significantly influenced by anxiety behavior unrelated to pain. Skin ARS was found to predict precisely current and future presence of pain, but could only predict a range of potential future pain scores based on the pain management approach in use during this study. Conclusions Skin ARS can provide valuable information for initiating preemptive analgesia and intensifying pain management during curative intent radiation therapy. Daily pain scoring with an acceptable pain scale should be used in conjunction with the skin ARS to improve patient pain management. Clinical relevance Pain is an anticipated consequence of curative intent radiation therapy. Understanding the correlation between pain and skin ARS may facilitate more effective pain management.