MP15-20: Survival after radical prostatectomy vs. Radiation therapy in ductal carcinoma of the prostate

Francesco Chierigo*, Genova, Italy, Christoph Würnschimmel, Hamburg, Germany, Rocco Simone Flammia, Rome, Italy, Benedikt Horlemann, Montreal, Canada, Gabriele Sorce, Milan, Italy, Benedikt Hoeh, Frankfurt, Germany, Zhe Tian, Fred Saad, Montreal, Canada, Markus Graefen, Hamburg, Germany, Michele Gallucci, Rome, Italy, Alberto Briganti, Francesco Montorsi, Milan, Italy, Felix K.H. Chun, Frankfurt, Germany, Shahrokh F. Shariat, Vienna, Austria, Guglielmo Mantica, Maro Borghesi, Nazareno Suardi, Carlo Terrone, Genova, Italy, Pierre I Karakiewicz, Montreal, Canada

Introduction: To compare cancer specific mortality (CSM) rates between radical prostatectomy (RP) vs. external beam radiotherapy (RT) in patients with ductal carcinoma (DC) of the prostate.

Methods: Within the Surveillance, Epidemiology, and End Results (SEER) database (2004-2016), we identified 369 DC patients, of whom 303 (82%) vs 66 (18%) were treated with RP vs RT, respectively. Kaplan-Meier plots and uni- and stepwise multivariate Cox regression models addressed CSM in the unmatched population. After propensity score matching (PSM) and inverse probability of treatment weighting (IPTW), Kaplan-Meier curve and Cox regression models tested the effect of RP vs RT on CSM.

Results: Overall, RT patients were older, harbored higher PSA values, higher clinical T and higher Gleason grade groups. 5-year CSM rates were respectively 4.2 vs 10% for RP vs RT (HR 0.40, 95% CI 0.16-0.99, p=0.048, favoring RP). At step-by-step multivariate Cox regression, after adding possible confounders, the central tendency of the HR for RP vs RT approached 1. PSM resulted into 124 vs 53 patients treated respectively with RP vs RT. After PSM, as well as after IPTW, the protective effect of RP was no longer present (HR 1.16, 95% CI 0.23-5.73, p=0.9 and  0.97, 95% CI 0.35-2.66, p=0.9, respectively).

Conclusions: Although CSM rate of ductal carcinoma RP patients is lower of that of RT patients, this apparent benefit disappears after statistical adjustment for population differences.

Source of Funding: no funding