Influence of Non-Index Pain Before Radiation Therapy for Bone Metastases on Post-Treatment QOL: Analyses Based on a Prospective Observational Study of 26 Centers.

Purpose: Although pain response is assessed based on the intensity of index pain (pain from the tumor targeted for radiation therapy), few studies have explored non-index pain (pain from other sites not targeted for radiation therapy). We examined the impact of pre-treatment non-index pain on quality of life (QOL) after radiation therapy.

Methods And Materials: Of 232 patients enrolled in the original prospective observational study conducted at 26 centers, 223 were analyzed. All enrolled patients received radiation therapy for pain due to bone metastases. QOL was measured using the EuroQol 5-dimensions 5-levels (EQ-5D-5L), the European Organization for Research and Treatment of Cancer (EORTC) QOL Questionnaire Core 15-Palliative (QLQ-C15-PAL), and the EORTC QOL Questionnaire Bone Metastases module (QLQ-BM22). Pain response was assessed based on the International Consensus Pain Response Endpoints.

Results: Non-index pain was present in 44%, 33%, and 39% of evaluable patients at baseline, 2 months, and 6 months, respectively. Non-index pain at baseline was associated with persistent non-index pain at 2 months (odds ratio, 4.92; 95% confidence interval, 2.42-10.32; P < 0.001). Patients who had non-index pain at baseline were significantly less likely to report a pain response at 2 months than those without it (odds ratio, 0.47; 95% confidence interval, 0.24-0.91; P = 0.021). The presence of non-index pain at baseline was significantly associated with worse QOL in terms of utility (P = 0.003) and the global health status/QOL (P = 0.005) and physical functioning (P = 0.008) scales of the QLQ-C15-PAL at 2 months. The presence of non-index pain at baseline was significantly associated with worse overall survival (P = 0.008).

Conclusions: The presence of non-index pain at baseline was significantly associated with a lower likelihood of pain response, worse QOL, and shorter survival following radiation therapy. Evaluation of both non-index and index pain is desirable in future studies on palliative radiation therapy for bone metastases.