Lymph node density predicts recurrence and death after inguinal lymph node dissection for penile cancer

PURPOSE To determine the impact of lymph node density (LND) on survival after inguinal lymph node dissection (ILND) for penile cancer. MATERIALS AND METHODS Our institutional penile cancer database was queried for patients who underwent ILND. Clinicopathologic characteristics including LND and total number of positive lymph nodes (LNs) were analyzed to determine impact on recurrence-free survival (RFS) and overall survival (OS). LND, or the percent of positive LN out of total LN, was calculated as a categorical variable at varying thresholds. RESULTS Twenty-eight patients with complete follow-up were identified. Indications for ILND were stage >T2 in 20 patients (71.4%), palpable adenopathy in 7 (25%), high grade T1 in 1 (3.6%). Median node yield was 17.5 (interquartile range, 12-22), and positive LNs were found in 14 patients (50%). RFS and OS were significantly lower for patients with >15% LN density (median RFS: 62 months vs. 6.3 months, p=0.0120; median OS: 73.6 months vs. 6.3 months, p<0.001). Controlling for age, medical comorbidities, number of positive LN, T stage, pelvic LN status and indication, LN density >15% was independently associated with worse RFS (hazard ratio [HR], 3.6; p=0.04) and OS (HR, 73.6; p=0.002). The c-index for LND was higher than total positive LNs for RFS (0.64 vs. 0.54) and OS (0.79 vs. 0.61). CONCLUSIONS In this small, retrospective penile cancer cohort, the presence of nodal involvement >15% was associated with decreased RFS and OS, and outperformed total number of positive LN as a prognostic indicator.