Background: Unlike lymph node (LN) staging in other malignancies, prostate cancer nodal staging does not characterize or quantify the LN tumor burden. Detailed characterization of LN metastases may provide improved prognostic information, which could assist in post-surgical management decisions. Methods: Clinical and pathologic information was retrospectively collected via electronic medical record from 66 patients with pathologically confirmed LN involvement after radical prostatectomy with pelvic lymph node dissection performed by a single surgeon. Tissue slides of all positive LNs were re-evaluated by a single pathologist in accordance with our institutional review board protocol. Poisson regression analyses and Cox proportional-hazard regression were performed to evaluate the association of risk factors with the number of positive nodes and the association of LN characteristics with biochemical recurrence (BCR)-free survival. Results: Median number of positive LNs per patient was 2 (IQR 1-3). Mean % positive LNs per patient was 8.9 (SD10.4). Mean cumulative size of all tumor deposits in all positive LNs per patient was 5.0mm (SD 4.8). Average % surface area of LN involved by tumor was 28%. 48 (73%) patients were alive without disease at median follow-up time of 38 months (IQR 26-50 months). Higher pre-surgery PSA, clinical stage T3-T4 versus T1-2, extraprostatic extension (EPE), seminal vesical involvement (SVI), and lymphovascular invasion (LVI) were significantly associated with higher incidence rate of nodal positivity. Larger mean size of largest LN deposits, mean size of total LN deposits, and mean % surface area of LN involved were significantly associated with worse BCR-free survival. There was no significant association for number of positive nodes, LN anatomical compartments, extranodal extension (ENE), span of ENE, and distance of ENE from LN capsule. Higher pre-surgery PSA and post-surgery Gleason grade were significantly associated with worse BCR-free survival. Conclusions: Our data shows that LN tumor burden is associated with worse BCR-free survival. Anatomical LN compartments and quantification of ENE did not show significant association with BCR.

Incidence Rate Ratio = IRR, Adjusted Hazard Ratio = aHR.