2548 - Comparing Pain Response to Palliative Radiotherapy in Painful Bone Metastases vs. Painful Non-Bone Lesions: A Secondary Analysis of a Prospective Observational Study

Y. Koide¹, Y. Shindo², N. Nagai¹, T. Kitagawa¹, T. Aoyama¹, H. Shimizu¹, S. Hashimoto¹, H. Tachibana¹, and T. Kodaira¹; ¹Department of Radiation Oncology, Aichi Cancer Center Hospital, Nagoya, Japan, ²Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan

Purpose/Objective(s): This study compared the pain response to palliative radiotherapy for bone metastases and non-bone lesions based on the International Consensus on Palliative Radiotherapy Effectiveness (ICPRE) criteria. Materials/

Methods: In our prospective observational study, 867 lesions from 500 patients undergoing palliative radiotherapy for a painful tumor between August 2021 and September 2023 were screened for this study, except for postoperative settings or brain metastases. The eligibility criteria were a numerical rating scale (NRS) of two or more before treatment. Information about pain sites, NRS, and opioid use was collected before treatment and 2, 4, 12, 24, 36, and 52 weeks later. The pain response was assessed based on the ICPRE criteria. The primary outcome was the pain response rate within 12 weeks, comparing two groups of patients with bone and non-bone lesions. A multivariate logistic regression analysis was conducted to adjust for confounding covariates based on opioid use, irradiation history, performance status, NRS, primary disease, and radiation dose. Statistical significance was defined as P<0.05.
Results: Among 678 lesions from 441 patients who met the criteria, the mean age was 63 years, and 45% were female. Treatment included conventional radiotherapy of a single 8 Gy dose, 20 Gy in 5 fractions, and 30 Gy in 10 fractions was used in 89% of lesions. With a median follow-up of 9.2 months, 270 patients had died. Painful bone metastases accounted for 541 lesions (80%), and the distribution of the 137 (20%) non-bone lesions of the primary lesions, lymph nodes, and other sites was 46/33/58. There were no differences in opioid use (67%) or re-irradiation rates (22%) between the two groups. Patients with non-bone lesions had a shorter median survival period than those with bone lesions (4.9 months vs. 6.3 months, P = 0.017) and were more frequently treated with fractionated irradiation (85% vs. 67%, P < 0.001). There were no differences in pain response rates between the two groups (57% vs. 62%, P = 0.33), and this remained consistent after adjusting covariates by a multivariate analysis (P = 0.19).
Conclusion: The results of this study suggest that palliative radiotherapy for pain response is effective not only for bone metastases but also for painful non-bone lesions. Future prospective clinical trials are awaited to determine the appropriate radiotherapy doses and fractions for painful non-bone lesions.