Optimizing the Threshold for Pelvic Lymph Node Dissection in the Contemporary Surgical Management of Prostate Cancer
Danielle A. Velez, MD; Ali Amin, MD; Jorge Pereira, MD; Paul Bower, MD; Dragan Golijanin, MD; Boris Gershman, MD; Joseph Renzulli, MD
Brown University / Rhode Island Hospital, Providence, RI
BACKGROUND: Pelvic lymph node dissection (PLND) is considered standard of care in the surgical management of intermediate and high-risk prostate cancer, but it is associated with potential morbidity. NCCN guidelines recommend PLND in patients with greater than 2% lymph node invasion (LNI) risk, but this threshold is controversial. To better balance the potential benefits and harms of PLND, we examined the relative diagnostic yields and complication rates at different LNI risk thresholds at our institution. METHODS: We performed a retrospective analysis of all robotic-assisted laparoscopic prostatectomies (RALP) with PLND from 2010 until 2016. Patients undergoing salvage RALP or cystoprostatectomy, receiving neoadjuvant therapy, and those with inadequate data to calculate the pre-RALP LNI risk using the MSKCC nomogram were excluded. Final pathology and rate of symptomatic lymphocele and deep vein thrombosis (DVT) were recorded. The pN1 diagnostic rate and PLND complications were evaluated at various PLND thresholds according to predicted risk of LNI.
RESULTS: The study cohort included 204 patients. The average number of lymph nodes removed was 11. The overall percentage of positive LNs was 15.2%. The balance of diagnostic yield and reduction in morbidity, including percentage of PLND avoided, across LNI risk thresholds is summarized in Table 1. Increasing the threshold for PLND from greater than 2% to greater than 5% would have avoided 22% of PLNDs, but this would have resulted in 9.68% of undetected pN1 disease. At the 5% threshold, four symptomatic lymphoceles and two DVTs would be avoided.
CONCLUSIONS: In our contemporary single institution series, increasing the PLND threshold from the currently recommended 2% to 5% reduced symptomatic lymphoceles by 31%, DVT by 33%, and the number of PLND by 22%, with only 9.68% of pN1 patients going undetected. At LNI risk of 5%, our data is within the accepted undiagnosed pN1 disease rate of less than 15%. Each complication adds to procedure morbidity, requiring invasive therapies or anticoagulation. Given the increased surgical risk and morbidity of a PLND, this data represents an opportunity for further research to validate a higher, PLND threshold.
| PLND Threshold: | > 2% | > 3% | > 4% | > 5% | > 6% | > 7% |
| # PLND | 195 | 176 | 167 | 159 | 144 | 130 |
| % PLND Avoided | 4% | 14% | 18% | 22% | 29% | 36% |
| % Undetected pN1 Disease | 0.0% | 9.7% | 9.7% | 9.7% | 16.1% | 19.4% |
| # SymptomaticLymphocele | 13 | 10 | 10 | 9 | 8 | 8 |
| # DVTs | 6 | 4 | 4 | 4 | 3 | 3 |
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