The impact of relationship between tumor volume and radiation dose on pain relief: are higher doses needed for larger tumors?

The influences of tumor volume and total radiation dose on pain relief outcomes have not been fully investigated. We investigated potential correlations between gross tumor volume (GTV), biologically effective dose (BED) and pain relief in patients receiving radiation therapy (RT) for painful tumors. As a secondary analysis of a three-center prospective observational study of 302 patients who received RT for painful tumors, patients treated at an academic hospital were analyzed. We used the Brief Pain Inventory short form to evaluate pain intensity and interference in patients' lives. We collected the Brief Pain Inventory and analgesic data at baseline and 1, 2, 3, 6, 9 and 12 months after the start of RT. Pain responses were assessed using the International Consensus Endpoint. The Fine and Gray models were used for univariable and multivariable analyses, to estimate the impact of clinical factors on pain response and pain progression. In total, 153 (59%) of the 258 patients experienced a pain response, and 45 (17%) patients experienced pain progression. In the univariable and multivariable analyses, GTV and BED did not significantly associate with pain response or pain progression. Furthermore, no significant interaction between GTV and BED was reported in terms of pain response or pain progression after adjusting for covariates. The impact of BED on pain response and pain progression did not vary according to the GTV.