Reduced survival of young patients under 55 years with metastatic prostate cancer: a population-based study

Objective: The aim of this study was to evaluate the prognosis of patients with metastatic prostate cancer (mPCa) in different age groups. Methods: Patients with mPCa from 2004 to 2016 in the Surveillance, Epidemiology and End Results (SEER) database were identified. Seven groups were divided according to the age at diagnosis, including ≤55 years, 56-60 years, 61-65 years, 66-70 years, 71-75 years, 76-80 years and >80 years. Fine and Gray's competing risks model and Kaplan-Meier analysis were conducted to evaluate the cancer-specific survival (CSS). Results: A total of 36231 patients with mPCa were included. The CSS curves of the overall cohort showed that patients aged ≤55 years had significantly worse CSS than patients in age groups of 56-60 [HR:0.93 (0.87~1.00), p=0.039], 61-65 [HR:0.91 (0.85~0.97), p=0.003] and 66-70 [HR:0.90 (0.84~0.96), p=0.001]. After removing patients dead for other reasons, the differences of CSS curves between ≤55 years group and 56-70 years groups were not significant. However, the mean survival time of ≤55 years group (55.78±2.48 months) was still shorter than 56-60 years (57.28±2.35 months), 61-65 years (57.64±2.07 months), and 66-70 years (57.11±2.11 months). When stratified by M stages, similar results were found in M1a, M1b and M1c stage groups. According to Fine-Gray competing risks models, patient ≤55 years featured significantly higher sub-distribution hazard ratio (sdHR) than 61-65 years group [sdHR: 0.94(0.88~1.00); p=0.046]. Conclusions: The mPCa patients ≤55 years seemed to be associated with worse prognosis in comparison with patients aging 56-70 years.