Pain as the evaluation criterion for bone metastasis radiosensitivity. Comparative efficacy of radiation therapy in patients with bone metastases of various primary tumors.

Abstract

Purpose: Assessment of the comparative radiosensitivity of bone metastases of various nature and histogenesis. Material/methods: As part of a randomized study, 810 courses of 3D-conformal or IMRT / VIMAT radiotherapy were performed for bone metastases of various origins and localization with persistent pain syndrome. Radiotherapy protocol included hypofractionation regimes of 2, 3 or 4 fractions of 6,5 Gy with total dose of 13-26 Gy or standard fractionation regime with total dose of 46 Gy. Results: The overall effectiveness (сomplete and partial pain relief) of radiotherapy was 96.2%, complete response rate (CRR) – 56.2%, partial response rate – 40.0%. Pain relapse rate was 8.6%, on average after 9.5 months after irradiation. The independent predictors of the CRR were: the initial pain intensity [hazard ratio (RR): 0.48, confidence interval (CI): 0.40-0.58; p = 0.0001], dose/number of fractions (RR: 1.26, CI: 1.07-1.50; p = 0.0059) and primary tumor site (RR: 0.95, CI: 0.92-0,99; p = 0.0053). We constructed a scale of comparative radiosensitivity of bone metastases of various primary tumors, taking into account the complete response rate and the probability of surviving without pain relapse for 6, 12 and 24 months after radiotherapy. The radiosensitive group included metastases from breast and prostate cancer, melanoma, bladder and PNET (CRR 60% or more), and relatively radioresistant group - metastases from unknown origin, colon, stomach and kidney cancer (CRR 40% or less). Conclusion: More than 95% overall effectiveness of radiotherapy for bone metastases, with pain relapse rate of less than 10% of cases, allows us to consider widefield irradiation in doses of 19.5-26 Gy, in 3-4 fractions of 6.5 Gy, the preferred treatment for multifocal lesions. Dose escalation in patients with bone metastases of kidney, colon, lung cancer and metastases from unknown origin seems to be justified in the cases with a life expectancy of more than a year.