Predictors of skeletal-related events and mortality in men with metastatic, castration-resistant prostate cancer: Results from the Shared Equal Access Regional Cancer Hospital (SEARCH) database

Background: Although skeletal-related events (SREs) are linked with a reduced quality of life and worse outcomes, to the authors' knowledge the factors that predict SREs are minimally understood. The objective of the current study was to identify predictors of SREs and all-cause mortality among men with metastatic castration-resistant prostate cancer (mCRPC). Methods: Data were collected on 837 men with bone mCRPC at 8 Veterans Affairs medical centers within the Shared Equal Access Regional Cancer Hospital (SEARCH) database from 2000 through 2017. Patients were followed to assess development of SREs (pathological fracture, radiotherapy to bone, spinal cord compression, or surgery to bone). Cox proportional hazards models were used to evaluate predictors of SREs and mortality. Results: Of the 837 men with bone mCRPC, 287 developed a SRE and 740 men died (median follow-up, 26 months). Bone pain was found to be the strongest predictor of SREs (hazard ratio [HR], 2.96; 95% CI, 2.25-3.89). A shorter time from CRPC to the development of metastasis (HR, 0.92; 95% CI, 0.85-0.99), shorter progression to CRPC (HR, 0.94; 95% CI, 0.91-0.98), and visceral metastasis at the time of diagnosis of bone metastasis (HR, 1.91; 95% CI, 1.18-3.09) were associated with an increased risk of SREs. Ten or more bone metastases (HR, 2.17; 95% CI, 1.72-2.74), undergoing radical prostatectomy (HR, 0.73; 95% CI, 0.61-0.89), shorter progression to CRPC (HR, 0.97; 95% CI, 0.94-0.99), older age (HR, 1.03; 95% CI, 1.02-1.04), higher prostate-specific antigen level at the time of diagnosis of metastasis (HR, 1.21; 95% CI, 1.14-1.28), bone pain (HR, 1.44; 95% CI, 1.23-1.70), and visceral metastasis (HR, 1.72; 95% CI, 1.23-2.39) were associated with an increased mortality risk. Conclusions: Among men with bone mCRPC, bone pain was found to be the strongest predictor of SREs and the number of bone metastases was a strong predictor of mortality. If validated, these factors potentially may be used for risk stratification and for SRE prevention strategies.