Risk Score to Identify Optimal Patients for Adjuvant RT After Radical Prostatectomy

New research presented at the 2024 American Urological Association Annual Meeting highlighted the development of a novel risk score to identify optimal candidates for early intensification approaches to adjuvant radiotherapy (RT) or salvage RT for node-positive patients with prostate cancer receiving radical prostatectomy (RP).

The optimal timing for postoperative RT remains unknown for patients with prostate cancer undergoing radical RP. Previous research suggests that early salvage RT is not inferior to adjuvant RT. While retrospective analyses suggest a survival benefit associated with adjuvant RT in patients with pN1 disease, it’s likely that only a few of these patients might benefit from adjuvant RT, given the heterogenous nature of pN1 disease.

A group of international researchers sought to design a novel risk score model to better understand which patients would benefit from adjuvant RT. A total of 751 patients with pN1 disease treated with RP and extended pelvic lymph node dissection at 19 care centers from 2006 to 2021 were sampled. Patients who received early salvage RT, defined as RT administered at prostate-specific antigen ≤0.5 ng/ml, were selected.

Multivariable Cox regression (MCR) models were utilized to assess the impact of pathological characteristics on overall mortality. A score was assigned to each pathological feature according to MCR coefficients, and then patients were stratified into low- (0-2 points), intermediate- (4-6), and high-risk (>6) groups.

After 3 months of landmark analysis, multivariable models tested for the impact of adjuvant RT within each risk group. Adjustment variables consisted of androgen-deprivation therapy (ADT) use (none, adjuvant ADT, and salvage ADT).

Among the patient sample, 43% (n=318) received adjuvant RT. In the MCR models, greater than 2 positive lymph nodes correlated with the strongest predictor of overall mortality (hazard ratio [HR], 3.4; 95% CI, 1.8-6.6; P<.001).

After stratification according to MCR scores, 197 (26%), 336 (45%), and 218 (29%) patients were included in the low-, intermediate-, and high-risk groups, respectively. This stratification scheme demonstrated a discrimination C index of 76%.

The 7-year overall rates for adjuvant RT versus observation with or without early salvage RT were 100% and 92%, 89% and 89%, and 84% and 73% in the low-, intermediate-, and high-risk groups, respectively. After landmark analysis, adjuvant RT independently predicted lower overall mortality in the high-risk group only (HR, 0.37; 95% CI, 0.14-0.93; P=.03), researchers concluded.