Assessing the Risk of Pathologic Lymph Node Involvement in Intermediate Risk Prostate Cancer

Abstract

Most intermediate risk (IR) prostate cancer (PCa) patients are predicted to have low rates of pelvic lymph node (PLN) involvement. The standard of care for radiation therapy in IR disease includes radiation to the prostate only, with PLN irradiation typically reserved for high-risk disease. This treatment strategy represents a divergence from the surgical approach, wherein PLN dissections (PLND) are recommended by NCCN guidelines for men with 2% or higher risk of nodal metastasis-a threshold typically met by men with IR disease. We conducted an analysis of radical prostatectomy (RP) patients to assess the rates of pathologic nodal involvement in IR disease. We aimed to evaluate the correlation of the NCCN risk strata of favorable and unfavorable disease on nodal outcomes among IR men treated by radical prostatectomy (RP).This is a National Cancer Database (NCDB) analysis from 2004-2015 of IR PCa patients treated by RP. Baseline clinical and demographic data were collected, and men were stratified into favorable and unfavorable risk groups. Treatment information assessed included performance of PLND at the time of surgery, number of nodes dissected, and pathologic outcomes at RP. The primary outcome of interest was the rate of pathologic nodal involvement.A total of 295,819 patients were identified in NCDB with IR PCa who underwent RP. Using NCCN risk stratification criteria, 147,193 (49.8%) men were identified with favorable intermediate risk (FIR) disease and 148,626 (50.2%) with unfavorable intermediate risk (UIR) disease. 90,410 (61.4%) FIR patients underwent pelvic node dissection compared to 107,135 (72.1%) UIR patients. Of the 189,304 (64.0%) total men who underwent PLND, 1.9% had pathologically involved nodes, with a rate of 0.7% for FIR disease and 2.8% for UIR (P < 0.001). The median [IQR] number of nodes resected on pelvic node dissection was 3[2-4] and 5[3-7] for FIR and UIR, respectively (P < 0.0001). Initial PSA > 5, Gleason pattern 4 on biopsy, and UIR disease were associated with pathologic nodal involvement (P < 0.0001).NCCN-defined FIR and UIR strata are associated with risk of PLN disease. The low number of nodes assessed on PLND may have contributed to the low rates of pathologic nodal involvement in IR PCa patients seen in this large database analysis. Even so, the low rates of pathologic nodal disease in this IR cohort, especially in FIR patients, should be considered in conjunction with upcoming clinical trial data to inform the therapeutic approach to PLN management for all intermediate risk patients undergoing surgery or radiation.