The Impact of Lymph Node Metastases Burden at Radical Prostatectomy

BACKGROUND: We hypothesized that a cut-off in positive lymph node (LN) counts may discriminate between cancer-specific mortality (CSM) rates in clinically localized prostate cancer patients treated with radical prostatectomy (RP).

OBJECTIVE: To test this relationship, we relied on different LN count cut-offs, as well as the continuously coded number of positive LNs (NPN).

METHODS: Within the Surveillance, Epidemiology, and End Results database (2004-2014), we identified patients with D'Amico intermediate- or high-risk characteristics who underwent RP and pelvic LN dissection, regardless of pathologic LN stage. Kaplan-Meier analyses and multivariable Cox regression models tested the effect of LN invasion (LNI) on CSM, according to the NPN.

RESULTS: Of 30016 patients treated with RP, 6.2% (n=1869) exhibited LNI, with respectively higher rates of LNI in patients with D'Amico high- versus intermediate-risk characteristics (11.6% vs 3.4%). Overall, the median age was 63yr, median prostate-specific antigen value was 6.6ng/ml and the median number of removed LNs was six. At 60 mo after RP, CSM rates were, respectively, 6.0% versus 0.8% for patients with and without LNI: multivariable hazard ratio (HR) 4.4 (p<0.001). CSM rates were, respectively, 0.8% for NPN 0, 2.4% for NPN 1-2 (HR: 3.5, p<0.001), and 7.2% for NPN ≥3 (HR: 10.3, p<0.001).

CONCLUSIONS: The NPN is an independent predictor of higher CSM rate. Specifically, patients with one to two positive LNs are at moderately higher risk of CSM than those without LNI, and CSM risk increases sharply in those with ≥3 positive LNs. Our contemporary findings corroborate the NPN cut-offs within previous studies.

PATIENT SUMMARY: Patients with three or more positive lymph nodes at radical prostatectomy have significantly higher cancer-specific mortality rates than those without or one to two positive lymph nodes. This stratification can be useful in considering adjuvant treatment options.