Independent External Validation of a Score Predicting Survival After Radiotherapy for Bone Metastases and Expansion to Patients Treated With Single Fraction Radiotherapy

BACKGROUND: Recently a prognostic score that predicts 12-month survival in patients treated with fractionated radiotherapy for painful bone metastases has been developed. Fractionated radiotherapy might cause unnecessary burden for patients with limited survival, thus estimation of survival is clinically relevant. The purpose of the present study was independent external validation of the new score and, in addition, its application in patients who received single fraction irradiation, a convenient option currently endorsed in several guidelines. METHODS: We conducted a retrospective analysis of 270 patients, including 24% who had received single fraction irradiation. The three-tiered score was assigned as described in the development study, and included age, performance status and primary tumor type. Additional prognostic factors not studied in the development cohort, such as the Glasgow prognostic score (GPS) and presence of liver metastases, were included in this validation study. RESULTS: The three-tiered score was valid in this independent cohort (12-month survival rates were 7%, 30% and 71%, respectively, P = 0.0001). Its performance and validity were also confirmed in the single fraction radiotherapy group. Three additional prognostic factors were significant in the multivariate analysis and may therefore contribute to decision making. CONCLUSIONS: Irrespective of fractionation, the score based on age, performance status and primary tumor type provides a readily available estimate of 12-month survival.