The role of adjuvant radiation in advanced penile cancer (PC) is unknown. We used the National Cancer Database (NCDB) to determine factors associated with receiving adjuvant radiation (aXRT) and their influence on prognosis in men who underwent inguinal lymph node dissection (ILND) for stage III disease.

We queried the NCDB from 1998-2012 for all men with PC who had pathologic nodal status and aXRT data available. Clinical and pathologic variables associated with aXRT were examined using chi-square testing. Logistic regression evaluated the odds of receiving aXRT while multivariate Cox regression analysis evaluated the influence of aXRT on overall survival (OS).

A total of 589 patients underwent ILND for stage III PC with 23% (N = 136) receiving aXRT. Mean age was 61.8 ±13.7 years. Factors associated with receiving aXRT included higher pathologic nodal stage (MV OR 1.85, 95% CI: 1.13-3.05), while greater distance of travel (MV OR 0.48, 95% CI: 0.25-0.92), and treatment in an academic setting (MV OR 0.53, 95% CI: 0.35-0.81) were inversely associated with receiving aXRT. On Cox regression analysis, aXRT improved OS (combined HR 0.58, 95% CI: 0.39-0.86), which appeared to have been driven by higher nodal burden (N2: HR 0.53, 95% CI: 0.32-0.88; N1: HR 1.36, 95% CI: 0.60-3.09).

Determinants of aXRT delivery in stage III PC appear to be related to the proximity to community cancer centers and greater nodal burden. We find evidence of a survival benefit with the use of aXRT, particularly in those with higher nodal stage. Multi-institutional studies are needed to confirm these findings and improve treatment algorithms for high-stage PC.