Extent of lymph node dissection improves survival in prostate cancer patients treated with radical prostatectomy without lymph node invasion

Abstract

Purpose: To assess the effect of pelvic lymph node dissection (PLND) extent on cancer-specific mortality (CSM) in prostate cancer (PCa) patients without lymph node invasion (LNI) treated with radical prostatectomy (RP).

Methods: Within the Surveillance, Epidemiology, and End results (SEER) database (2004-2014), we identified patients with D'Amico intermediate- or high-risk characteristics who underwent RP with PLND, without evidence of LNI. First, multivariable logistic regression models tested for predictors of more extensive PLND, defined as removed lymph node count (NRN) ≥75th percentile. Second, Kaplan-Meier analyses and multivariable Cox regression models tested the effect of NRN ≥75th percentile on CSM. Finally, survival analyses were repeated using continuously coded NRN.

Results: In 28 147 RP and PLND patients without LNI, 67.3% versus 32.7% exhibited D'Amico intermediate- or high-risk characteristics. The median NRN was 6 (IQR 3-10), the 75th percentile defined patients with NRN ≥11. Patients with NRN ≥11 had higher rate of cT2/3 stage (29.8 vs 26.1%), GS ≥8 (25.7 vs 22.4%), and respectively more frequently exhibited D'Amico high-risk characteristics (34.6 vs 32.1%). In multivariable logistic regression models predicting the probability of more extensive PLND (NRN ≥11), higher biopsy GS, higher cT stage, higher PSA, more recent year of diagnosis, and younger age at diagnosis represented independent predictors. At 72 months after RP, CSM-free rates were 99.5 versus 98.1% for NRN ≥11 and NRN ≤10, respectively and resulted in a HR of 0.50 (P = 0.01), after adjustment for all covariates. Similarly, continuously coded NRN achieved independent predictor status (HR: 0.955, P = 0.01), where each additional removed lymph node reduced CSM risk by 4.5%.

Conclusion: More extensive PLND at RP provides improved staging information and consequently is associated with lower CSM in D'Amico intermediate- and high-risk PCa patients without evidence of LNI. Hence, more extensive PLND should be recommended in such individuals.

Keywords: SEER registry; cancer-specific survival; lymph node dissection; prostate cancer; radical prostatectomy.