Radiosensitivity of metastases in the skeleton of tumors with different primary site
The purpose of the current clinical trial was to evaluate efficiency of palliative external beam radiotherapy for symptomatic bone metastases from different primary tumors. The randomized study included 427 patients, treated for 616 sites of bone lesions. Breast was the primary site in 67,5% of cases, prostate and lung - in 7,5% each, renal - in 5,5%, other tumors - in 12%. The most frequent treatment site was the spine - 47,8%, followed by pelvis - 30,8%, long bones - 14,4%, sacrum - 2,9% and other sites - 4%. The main indication for irradiation was pain not alleviated by systematic drug therapy. Radiotherapy protocol included 3 hypo-fractionation regimes with total dose of 26 Gy, 19,5 Gy and 13 Gy by 3, 4 and 2 fractions of 6,5 Gy correspondingly and standard treatment schedule with total dose of 26 Gy. The average follow-up period was 56 months. General pain relief (complete and partial) was observed in 96,1% of sites and was independent of primary tumor, metastases localization and irradiation schedules. Complete response rate (CRR) was higher for bone metastases form breast and prostate cancer 64,2% and 58,7% correspondingly in comparison with lung and renal cancer - 43,5% and 26,5% respectively (р<0,05). At small number of observations metastases from melanoma and sarcomas proved high radiosensitivity with CRR. 75% and 66,7% correspondingly. CRR. for spine and pelvis localization of metastases was similar - 63,4% and 59,3%, slightly lower for long bones - 48,3% and significantly lower for sacrum isolated metastases - 27,8% (р<0,05). CRR. was higher for standard treatment schedule and significantly increased for 2, 3 and 4 fractions of 6,5 Gy correspondingly (p<0,03). In the multifactorial analysis tumor primary site and pain intensity before radiotherapy were the only independent prognostic factors of CRR. Therefore histogenesis of primary tumor is a predictor of radiosensitivity of bone metastases, it significantly affects the complete pain response rate. It is expedient to use hypofractionation regimes of 3 fractions of 6,5 Gy (total dose 19,5 Gy) for palliative radiotherapy of bone metastases in case of breast, prostate cancer, sarcomas and melanoma and 4 fractions of 6,5 Gy (total dose 26 Gy) in case of lung and renal cancer.