Development and external validation of lymph node density cut-off points in prospective series of radical cystectomy and pelvic lymph node dissection

Objective: To identify lymph node density thresholds and their prognostic role in patients who underwent radical cystectomy and pelvic lymph node dissection, and to validate findings in an external series. Methods: Between May 2001 and September 2009, data from 750 radical cystectomies carried out at "Regina Elena" National Cancer Institute (Rome, Italy) were collected in a prospectively-maintained database. Once patients who had undergone neoadjuvant treatments and those who had undergone salvage radical cystectomy were excluded from the 210pN+ patients, 156 patients with urothelial carcinoma were selected for analysis. Optimal cut-off points for age, lymph node count and lymph node density were identified by considering these variables as continuous. External validation of findings was carried out by using data of 154pN+ patients selected from two prospective series. Results: The optimal identified cut-off points were 11% and 30% for lymph node density, nine and 30 nodes for lymph node count, and 73years for age. Median cancer-specific survival of patients were significantly different in patients with lymph node density 30% (71months, 24months and 11months, respectively; P30% vs 30% vs