Introduction

The role of post-prostatectomy radiation therapy (RT) in patients with pN1 prostate cancer is still under debate. However, whether adjuvant RT (aRT) is equal to early salvage RT (esRT) at long term in this setting is still unknown. In this study, we aimed at comparing the long-term effectiveness of aRT versus esRT.

Methods

Using a multi-institutional cohort from six tertiary referral centres, we identified 171 pN1 patients who were treated with radical prostatectomy and pelvic lymph node dissection. Patients were stratified into two groups: aRT (Group 1) versus initial observation followed by esRT in case of PSA relapse (Group 2). Specifically, aRT was administered at undetectable PSA level within 6 months after RP, whereas esRT was administered at a PSA level ≤0.5 ng/ml. The clinical target volume included the pelvic lymph nodes area, prostatic and seminal vesicle bed in all patients receiving RT. The evaluated outcomes were metastasis-free and overall survival. Multivariable Cox regression analyses tested the association between groups (aRT vs. observation ± esRT) and the study outcomes. Covariates consisted of pathologic stage (≤pT3a vs. ≥pT3b), pathologic Gleason score (≤7 vs. ≥8), and surgical margin status (negative vs. positive).

Results

Overall, 85 (50%) and 86 (50%) patients underwent aRT and initial observation, respectively. Median follow-up was similar among groups: 84 vs. 92 months (p=0.9). In group 2, 69 (80%) patients experienced PSA relapse and underwent esRT. Patients characteristics were not significantly different in terms of pathologic stage (≥pT3b: 60% vs. 53%, p=0.2), Gleason score (≥8: 44% vs. 41%, p=0.9), and positive surgical margins (59% vs. 55%, p=0.6). Overall, 26 patients developed distant metastasis with the following distribution: retroperitoneal nodes (n=5), bone (n=19), and other organs (n=2). At last follow-up, 13 patients succumb to prostate cancer and 13 patients died for other cause. Metastasis-free survival (67% vs. 72% p=0.2) and overall survival (78% vs. 74%, p=0.8) at 8 years after RP were not significantly different among groups. These results were confirmed at multivariable analyses for both distant metastasis (HR: 0.77; p=0.7) and overall survival (HR: 1.94; p=0.3).

Conclusions

At long-term follow-up, timely administration of esRT showed comparable metastasis-free and overall survival to aRT. Even in pN1 patients, esRT may not thus compromise cancer control, while significantly reducing potential over-treatment associated with aRT.

Funding

none