Worst, average or current pain in the brief pain inventory: Which should be used to calculate the response to palliative radiotherapy in patients with bone metastases?

Aims: To determine which pain intensity scale in the Brief Pain Inventory correlates best with functional interference and should be used to calculate the response to palliative radiotherapy. To determine the differences in functional interference scores for patients classified as responders and non-responders to palliative radiotherapy. Patients and methods: All patients referred to the Rapid Response Radiotherapy Program for palliative radiotherapy of symptomatic bone metastases were considered for the study. Patients rated the intensity and functional interference of their pain at the irradiated sites according to the Brief Pain Inventory before and 2 months after radiotherapy. Worst, average and current pain scores were correlated with functional interference scores using Spearman rank coefficients. Responders and non-responders to palliative radiotherapy were defined for each pain intensity scale according to the end points specified by the International Bone Metastases Consensus Working Party. Average differences between responders and non-responders were compared using a Wilcoxon rank sum test. Results: Between May 2003 and June 2005, 199 patients enrolled in the study (102 men and 97 women). Ninety-five patients returned complete questionnaires at 2 months of follow-up. All pain intensity and interference scores for evaluable patients were significantly lower at 2 months (P < 0.0021). Response rates differed depending on the definition of pain intensity. An overall response rate was observed in 66, 58 and 54% of patients for worst, average and current pain, respectively. Worst pain showed the best correlation with functional interference. Responders reported significantly larger decreases in functional interference scores at follow-up in general activity, normal work, enjoyment of life and average functional interference. Conclusion: Worst pain intensity had higher correlations with all functional interference scores except relationships with others. Therefore, we recommend an 11-point scale measuring worst pain to evaluate response rates in future radiotherapy trials. The mean difference from baseline to follow-up in functional interference scores was significantly larger in patients who responded to radiotherapy treatment.