Prognostic factors and a new scoring system for survival of patients irradiated for bone metastases

Background: Personalized therapy for bone metastases should consider the patients' remaining lifespan. Estimation of survival can be facilitated with scoring tools. A new tool was developed, specifically designed to estimate 12-month survival. Methods: In 445 patients irradiated for bone metastases, radiotherapy regimen plus 13 factors (age, gender, Karnofsky performance score (KPS), primary tumor type, interval between cancer diagnosis and RT of bone metastases, visceral metastases, other (non-irradiated) bone metastases, sites of bone metastases, number of irradiated sites, pathological fracture, fractionation of RT, pre-RT surgery, pre-RT administration of bisphosphonates/denosumab, pre-RT systemic anticancer treatment) were retrospectively analyzed for survival. Factors achieving significance (p < 0.05) or borderline significance (p < 0.055) on multivariate analysis were used for the scoring system. Twelve-month survival rates were divided by 10 (factor scores); factor scores were summed for each patient (patient scores). Results: On multivariate analysis, survival was significantly associated with KPS (hazard ratio (HR) 1.91, p < 0.001) and primary tumor type (HR 1.12, p < 0.001); age achieved borderline significance (HR 1.14, p = 0.054). These factors were used for the scoring tool. Patient scores ranged from 8 to 17 points. Three groups were designated: 8-9 (A), 10-14 (B) and 15-17 (C) points. Twelve-month survival rates were 9, 38 and 72% (p < 0.001); median survival times were 3, 8 and 24 months. Conclusions: This new tool developed for patients irradiated for bone metastases at any site without spinal cord compression allows one to predict the survival of these patients and can aid physicians when assigning the treatment to individual patients.