Impact of Adjuvant Radiotherapy in Node-positive Prostate Cancer Patients: The Importance of Patient Selection

Using institutional data, we have previously developed an algorithm to identify the optimal candidates for adjuvant radiotherapy (aRT) among men with pN1 prostate cancer (PCa) at radical prostatectomy (RP). This study aimed to test the external validity of our previous findings using a nationwide database while focusing on overall mortality as an endpoint. To this end, we identified 5498 pN1 PCa patients who were treated with RP, pelvic lymph node dissection, and androgen deprivation therapy with or without aRT, within the National Cancer Database, between 2004 and 2015. Patients were divided into five groups based on our previously published algorithm. Similar to our previous report, multivariable Cox regression analysis showed that only two of these groups benefit from aRT: (1) those with one to two positive nodes, pathological Gleason score 7-10, and pT3b/4 disease or positive surgical margins (hazard ratio [HR]=0.75); and (2) those with three to four positive nodes, regardless of local tumor characteristics (HR=0.57, both p=0.01). In the remaining patients (25% of the cohort), aRT had no significant survival benefit. Results were confirmed on sensitivity analyses using 1:1 propensity score-matched cohorts, excluding men who died within 3 yr of surgery and using cut-off of 6 mo post-surgery to identify receipt of aRT. Our findings corroborate the validity of our previously published criteria and highlight the importance of patient selection in pN1 PCa patients who are considered for aRT.