Cancer-specific survival after metastasis following primary radical prostatectomy compared with radiation therapy in prostate cancer patients: Results of a population-based, propensity score-matched analysis

Background Data regarding the difference in the clinical course from metastasis to prostate cancer-specific mortality (PCSM) following radical prostatectomy (RP) compared with radiation therapy (RT) are lacking. Objective To examine the association between primary treatment modality and prostate cancer-specific survival (PCSS) after metastasis. Design, setting, and participants We used the Surveillance Epidemiology and End Results-Medicare linked database from 1994 to 2007 for patients diagnosed with localized prostate cancer (PCa). We used cancer stage and Gleason score to stratify patients into low and intermediate-high risks. Intervention Radical prostatectomy or radiation therapy. Outcome measurements and statistical analysis Our outcome is time from onset of metastases to PCSM. Propensity score matching and Cox regression were used to analyze the PCSM hazard for the RP group compared with the RT group. Results and limitations Our study consisted of 66 492 men diagnosed with PCa, 51 337 men receiving RT, and 15 155 men undergoing RP within 1 yr of cancer diagnosis. During the study period, 2802 men were diagnosed as having metastatic disease. A total of 916 men with metastases were included in the propensity-matched cohort; of these men, 186 died from PCa. During the follow-up, for the low-risk patients, the adjusted PCSS after metastasis was 86.2% and 79.3% in the RP and RT groups, respectively; for the intermediate-high-risk patients, the PCSS after metastasis was 76.3% and 63.3% in the RP and RT groups, respectively. The hazard ratios estimating the risk of PCSM between the RP and RT groups were 0.64 (95% confidence interval [CI], 0.36-1.16) and 0.55 (95% CI, 0.39-0.77) for the low- and intermediate-high-risk groups, respectively. Because of the nature of observational studies, the results may be affected by residual confounders and treatment indication. Conclusions Following the development of metastases, men who received primary RP have a longer PCSS than men who received primary RT. Our results may have implications for the timing and nature of local PCa treatment.