Survival benefit of definitive therapy in patients with clinically advanced prostate cancer: estimations of the number needed to treat based on competing-risks analysis

Objective To describe the survival benefit associated with radical prostatectomy (RP), as compared with initial observation, in patients with locally advanced prostate cancer (PCa).Patients and Methods Overall, 1382 patients with locally advanced PCa treated with RP or initial observation between 1995 and 2009 were identified from the Surveillance, Epidemiology and End Results Medicare insurance programme-linked database. Patients were matched using propensity-score methodology, then 10-year cancer-specific mortality (CSM) rates were estimated and the number needed to treat (NNT) was calculated. Competing-risks regression analyses tested the relationship between treatment type and CSM.Results Overall, the 10-year CSM rates were 11.8 and 19.3% for patients treated with RP and initial observation, respectively (P < 0.001). The corresponding 10-year NNT was 13. The 10-year CSM rates for the same treatment groups were 8.9 vs 13.9%, respectively, for Gleason score ≤7, 16.8 vs 27.8%, respectively, for Gleason score 8-10, 10.1 vs 15.8%, respectively, for clinical stage T3a, and 17.0 vs 29.3%, respectively, for T3b/T4, respectively (all P ≤ 0.04). The corresponding NNTs were 20, 9, 17 and 8, respectively. In multivariable analyses, RP was an independent predictor of more favourable CSM rates in all categories (all P ≤ 0.04). In separate sensitivity analyses, no differences were recorded when patients treated with radiotherapy were compared with those receiving RP (P = 0.4). Conversely, patients undergoing initial observation had a higher risk of CSM compared with those treated with radiotherapy (P = 0.03).Conclusions RP leads to a significant survival advantage compared with observation in patients with locally advanced disease. The highest benefit was observed in patients with T3b/T4 and Gleason score 8-10 disease.