Clinical features and efficacy of radiotherapy for bone metastases of unknown origin

Abstract

Purpose: to study the efficiency of radiotherapy for bone metastases of unknown origin. Material and methods: Of 686 cases of bone metastases included in the long-term randomized trial in 16 (2,4%) it was impossible to identify the primary tumor site. The most frequent primary site was breast - 62,1%, prostate and lung cancer were diagnosed in 8,3%, renal cancer in 6,9%, colon cancer in 2,6%. Separately we analyzed the mixed group of 19 patients represented by rare cases of bone metastases of stomach and liver cancer, head and neck tumors, gynecological tumors («Others). Patient selection criteria for radiotherapy were pain, risk of pathological fracture/malignant spinal cord compression, increasing neurologic dysfunction. Irradiation volume included one anatomical area of the skeleton. Total dose was 13-26Gy in 2-4 fractions of 6,5 Gy. Results: The average follow-up period was 70 months. The main characteristics of bone metastases of unknown origin such as gender, age, lesion length, risk of pathological fracture, pain intensity before treatment and effectiveness of EBRT were similar to the bone metastases of colon cancer and to the group «Others. Overall effectiveness of EBRT (complete and partial pain relief) for bone metastases of unknown origin was 81,2%, complete response rate attained in 43,8% of cases. Relative pain reduction was 65,4% and turned out to be one of the lowest between analyzed groups. It was significantly lower for bone metastases of unknown origin compared to breast cancer and melanoma (82,7% and 88,9%, p<0,05). The results of the study make it possible to classify metastases in the skeleton of unknown origin as radioresistant lesions as well as bone metastases of renal, lung and colon cancer.