Session Item

The search for evaluation criterion for the radiosensitivity of metastases in the skeleton and the assessment of the comparative radiosensitivity of bone metastases of various origins.

To identify the relationship between pain and other clinical symptoms, 810 cases of bone metastases with persistent pain syndrome were analyzed.  3D-conformal or IMRT / VIMAT radiotherapy was performed for bone metastases of various origins and localization. Radiotherapy protocol included hypofractionation regimes of 2, 3 or 4 fractions of 6,5 Gy with total dose of 13-26 Gy. The effectiveness of radiotherapy was assessed by the frequency of complete and partial pain relief, the degree of pain regression relative to baseline, the risk and timing of pain relapse.

The severity of pain directly correlated with gender, lesion length and little associated with pathological fracture. The intensity of pain did not depend on the primary tumor and bone metastases localization and did not correlate with the presence of neurological deficit. 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), the radioresistant group - metastases from unknown origin, colon, stomach and kidney cancer (CRR 40% or less). The scale of radiosensitivity is shown in Image.

Complete pain relief turned out to be the most significant clinical criterion for assessing the effectiveness of radiation therapy of bone metastases. Completeness and persistence of the analgesic effect may reflect the real radiosensitivity of bone metastases. More than 95% overall effectiveness of radiotherapy for bone metastases, with pain relapse rate of less than 10% of cases, allows us to consider 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.