Characterization of Lymph Node Tumor Burden in Node-Positive Prostate Cancer Patients after Robotic-Assisted Radical Prostatectomy with Extended Pelvic Lymph Node Dissection

SIMPLE SUMMARY: Prostate cancer (PCa) nodal staging does not account for tumor burden within the lymph nodes (LNs). In this retrospective single institution/single surgeon study, we assessed the significance of LN tumor burden in pN1 PCa patients after undergoing robotic-assisted radical prostatectomy with extended pelvic lymph node dissection. Consistent with prior reports, LN tumor burden was found to be significantly associated with biochemical recurrence-free survival (BRFS). This study was the first to report on the significance of the anatomical location of tumor deposits within the LN, as well as the quantified extent of extranodal extension (ENE). Likely due to sample size, the anatomical location within the LN and ENE did not show significant association with BRFS. We emphasize that PCa nodal staging and/or post-operative clinical nomograms should account for LN tumor burden. ABSTRACT: Background: Prostate cancer (PCa) nodal staging does not account for lymph node (LN) tumor burden. The LN anatomical compartment involved with the tumor or the quantified extent of extranodal extension (ENE) have not yet been studied in relation to biochemical recurrence-free survival (BRFS). Methods: Histopathological slides of 66 pN1 PCa patients who underwent extended pelvic lymph node dissection were reviewed. We recorded metrics to quantify LN tumor burden. We also characterized the LN anatomical compartments involved and quantified the extent of ENE. Results: The median follow-up time was 38 months. The median number of total LNs obtained per patient was 30 (IQR 23–37). In the risk-adjusted cox regression model, the following variables were associated with BRFS: mean size of the largest LN deposit per patient (log2: adjusted hazard ratio (aHR) = 1.91, p < 0.001), the mean total span of all LN deposits per patient (2.07, p < 0.001), and the mean percent surface area of the LN involved with the tumor (1.58, p < 0.001). There was no significant BRFS association for the LN anatomical compartment or the quantified extent of ENE. Conclusion: LN tumor burden is associated with BRFS. The LN anatomical compartments and the quantified extent of ENE did not show significant association with BRFS.