EAU 2018: What is the Optimal Field of Post-Prostatectomy Radiation Therapy? Long-Term Results from a Multi-Institutional

Copenhagen, Denmark (UroToday.com) Approximately 30% of patients will experience a PSA recurrence following a radical prostatectomy. Local management of a PSA recurrences remains ill-defined with some advocating for prostate fossa radiation while orders recommend additional whole pelvis coverage. Given the increased risk of radiation side effects with whole pelvic radiation, so have advocated its use for those with a high risk of nodal recurrence. Unfortunately, there is a paucity of prediction models to accurately select patients at high risk of nodal involvement at the time recurrence, PSA doubling time being the most accurate. Dr. Chiordia, from Urologic Research Institute at San Raffaele, presents a retrospective review of patients undergoing focal and whole pelvis radiation with the aim to find pathological prediction markers to better select patients for each. 

The study included 732 patients from 7 referral centers who received either adjuvant RT (29%) or salvage RT (63%) or RT for a persistent elevated PSA (8%) following radical prostatectomy (RP). All patients received local radiation (prostatic fossa and seminal vesicle bed), while whole pelvic radiation was left at the discretion of the treating physician. The main outcome of the study was clinical recurrence seen on imaging. In the study, 67% received focal treatment with 33% receiving focal and whole pelvis radiation. At a median follow-up of 105 months, 131 patients developed a clinical recurrence. On multivariate modeling, receipt of whole pelvic radiation was associated with a lower risk of clinical recurrence (HR 0.73, p=-0.02). A prediction model for the prediction of clinical recurrence was was created using variables associated with clinical recurrence on multivariate modeling (pathologic stage (≤pT3a vs. ≥pT3b), Gleason score (≤7 vs. ≥8), number of lymph nodes removed, PSA level at RT (ng/ml), RT dose (Gy), and concomitant HT administration (no vs. yes)). The predicted risk of recurrence was each patient was plotted against the recurrence risk at 10 years (Figure 1). On review of the plot, the benefit of whole pelvis radiation became significant when the risk of recurrence was 10% or higher (red line). 

In summary, in the post-prostatectomy setting whole pelvic radiation provides better cancer control than focal therapy when the risk of recurrence is 10% or greater based on a novel risk calculator.

Chiorda 1

Presented by: Noris Chiorda MD, Urological Research Institute - IRCCS Ospedale San Raffaele, Dept. of Radiotherapy, Milan, Italy

Written by: Andres F. Correa, Urologic Oncology Fellow, Fox Chase Cancer Center, Philadelphia, PA at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark.
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