Association of lymph node yield with overall survival in patients with pathologically node negative prostate cancer

We investigated the association between lymph node yield (LNY) with overall survival (OS) and post-radical prostatectomy (RP) secondary treatments among men with pathologically node negative (pN0) prostate cancer. We reviewed the National Cancer Database for men with Gleason Grade Group 2 or higher prostate cancer treated with RP and had pathologically node-negative disease. LNY was modeled as a continuous and categorical variable grouped by quartiles of LNY. Secondary treatment was defined as the use of radiation or systemic therapy post-RP. Multivariable Cox proportional hazards and logistic regression models were used to test for an association of LNY with OS and secondary treatments, respectively. We identified 89,416 men with pN0 prostate cancer treated with RP from 2010-2015. LNY was associated with improved OS when modeled as a categorical and continuous variable. The third (6-9 nodes) and fourth (≥10 nodes) quartiles of LNY were associated with improved OS (HR 0.87, 95% CI 0.79-0.96, P = 0.006 and HR 0.88, 95% CI 0.79-0.98, P= 0.017, respectively) when compared with the lowest quartile of LNY (≤3 nodes) and the hazard of death decreased by 1% for each benign lymph node removed (HR 0.99, 95% CI 0.98-0.99, P= 0.022). Additionally, categorical and continuous LNY was associated with significantly less use of post-RP secondary treatments. Removal of additional negative lymph nodes was associated with improved OS and less secondary treatments in patients with pN0 prostate cancer. These data suggest that removing a higher quantity of lymph nodes provides more accurate staging and prognosis.