Prognosis of patients with pelvic lymph node (LN) metastasis after radical prostatectomy: value of extranodal extension and size of the largest LN metastasis

Objective To assess the prognostic role of extranodal extension (ENE) and the size of the largest lymph node (LN) metastasis in predicting early biochemical relapse (eBCR) in patients with LN metastasis after radical prostatectomy (RP). Patients and Methods We evaluated BCR-free survival in men with LN metastases after RP and pelvic LN dissection performed in six high-volume centres. Multivariable Cox regression tested the role of ENE and diameter of largest LN metastasis in predicting eBCR after adjusting for clinicopathological variables. We compared the discrimination of multivariable models including ENE, the size of largest LN metastasis and the number of positive LNs. Results Overall, 484 patients were included. The median (interquartile range, IQR) follow-up was 16.1 (6-27.5) months. The median (IQR) number of removed LNs was 10 (4-14), and the median (IQR) number of positive LNs was 1 (1-2). ENE was present in 280 (58%) patients, and 211 (44%) had their largest metastasis >10 mm. Patients with ENE and/or largest metastasis of >10 mm had significantly worse eBCR-free survival (all P < 0.01). On multivariable analysis, number of positive LNs (≤2 vs >2) and the diameter of LN metastasis (≤10 vs >10 mm), but not ENE, were significant predictors of eBCR (all P < 0.003). ENE and diameter of LN metastasis increased the area under the curve of a baseline multivariable model (0.663) by 0.016 points. Conclusions The diameter of the largest LN metastasis and the number of positive LNs are independent predictors of eBCR. Considered together, ENE and the diameter of the largest LN metastasis have less discrimination than the number of positive LNs.