Little is known about the impact of adjuvant radiation therapy (aRT) after radical prostatectomy (RP) on urinary continence (UC).

To evaluate the impact of aRT on UC recovery in patients with unfavourable pathologic characteristics.

The study included 361 patients with either pT2 with positive surgical margin(s) or pT3a/pT3b node-negative disease treated with RP at a tertiary care referral centre.

Patients were stratified according to the administration of aRT into two groups: group 1 (no aRT; n=208; 57.8%) and group 2 (aRT; n=153; 42.2%).

Continence was defined as no use of protective pads. Log-rank test was used to compare the rate of UC recovery according to aRT status. The association between aRT and UC was also tested in Cox regression models after accounting for age, Cancer of the Prostate Risk Assessment (CAPRA) score, nerve-sparing (NS) status, Charlson Comorbidity Index, body mass index, and year of surgery.

At a mean follow-up of 30 mo, 254 patients (70.4%) recovered complete UC. The 1- and 3-yr UC recovery was 51% and 59% for patients submitted to aRT versus 81% and 87% for patients not receiving aRT, respectively (p<0.001). At univariable analysis, older age (p<0.001), presence of non-organ-confined disease (p<0.001), non-NS procedure (p<0.001), and delivery of aRT (p<0.001) were significantly associated with lower UC. At multivariable analysis, the delivery of aRT remained an independent predictor of worse UC recovery (hazard ratio: 0.57; p=0.001). Patients treated with aRT had a 1.6-fold higher risk of incontinence. Younger age (p=0.02), lower CAPRA score (p=0.03), and NS approach (p<0.001) also represented independent predictors of UC recovery. The main limitations of the study are related to the lack of validated questionnaires in the evaluation of UC and in the lack of information regarding UC status at aRT.

The delivery of aRT has a detrimental effect on UC. The oncologic benefits must be balanced with an impaired UC recovery. Patients should be informed of such impairment before adjuvant treatments are planned.