3360 - Impact of Extended Pelvic Lymph Node Dissection on Outcomes in High-Risk Prostate Cancer Patients Receiving Postoperative Pelvic Radiotherapy: A Secondary Analysis of a Prospective Study

Purpose/Objective(s): For localized high-risk or very-high-risk prostate cancer (PC), the NCCN guidelines recommend extended pelvic lymph node dissection (ePLND) during radical prostatectomy (RP). While ePLND provides accurate nodal staging and potentially reduces biochemical recurrence or distant metastasis, it carries a significant complication risk (up to 20%), including hemorrhage, thromboembolic event, lymphocele and lower limb edema. This study aimed to evaluate whether ePLND influences clinical outcomes in patients who already receive postoperative radiotherapy (PORT) including the pelvic lymph nodes.

Materials/Methods: Data were analyzed from a prospective cohort of patients treated at a single institution between 2017 and 2020. Inclusion criteria were: 1) post-RP PC patients; 2) NCCN localized high-risk or very-high-risk group; and 3) no evidence of nodal or distant metastasis (N0M0) prior to surgery. All patients received PORT targeting both the prostate bed and pelvic lymph node. Patients were categorized into two groups: those who underwent RP with ePLND and those without ePLND. Clinical outcomes were analyzed, including event-free survival (EFS), biochemical recurrence-free survival (bRFS), and regional recurrence-free survival (RRFS). Propensity score matching (PSM) was performed at a 1:1 ratio, adjusting for age, pre-operative PSA, T-stage, surgical margins, Gleason Score (GS), androgen deprivation therapy (ADT) use, and pre-radiotherapy PSA levels.

Results: A total of 326 patients were screened, with 195 high-risk/very-high-risk patients meeting the inclusion criteria for this analysis (64 with ePLND, 131 without). The median follow-up was 51 months. In the unmatched cohort, the ePLND group had a higher proportion of GS 9-10 (61.0% vs. 29.8%, p < 0.001) and ADT use (82.8% vs. 58%, p = 0.001). Despite these baseline differences, there were no significant differences in 5-year outcomes between the ePLND and no-ePLND groups: EFS (78.2% vs. 79.4%, p = 0.884), bRFS (84.9% vs. 88.7%, p = 0.838), and RRFS (90.9% vs. 98.9%, p = 0.653). After 1:1 PSM (n = 48 per group), baseline characteristics were well-balanced. The matched analysis showed no significant differences between the ePLND and no-ePLND groups for 5-year EFS (80.4% vs. 79.6%, p = 0.817) or 5-year bRFS (85.5% vs. 86.3%, p = 0.884). Both groups achieved a 5-year RRFS of 100.0%.

Conclusion: In patients with localized high-risk or very high-risk PC receiving postoperative pelvic radiotherapy, the addition of ePLND during RP does not appear to provide additional EFS, bRFS, or RRFS benefits. These findings suggest that for patients planned for postoperative pelvic irradiation, pelvic radiotherapy may serve as a viable alternative to ePLND, potentially achieving comparable disease control while avoiding the surgical morbidity associated with ePLND and improving quality of life.