Assessing the minimum number of lymph nodes needed at radical cystectomy in patients with bladder cancer

To identify the likelihood of finding one or more positive lymph nodes (LNs) according to the number of LNs removed at radical cystectomy (RC), as the number of LNs removed affects disease progression and survival after RC. Between 1984 and 2003, 731 assessable patients had RC and bilateral pelvic lymphadenectomy at three different institutions. ROC curve coordinates were used to determine the probability of identifying one or more positive LNs according to the total number of removed LNs. Of the 731 patients, 174 (23.8%) had LNs metastases. The mean (median, range) number of LNs removed was 18.7 (17, 1-80). The ROC coordinate-based plots of the number of removed LNs and the probability of finding one or more LNs metastases indicated that removing 45 LNs yielded a 90% probability. Conversely, removing either 15 or 25 LNs indicated, respectively, 50% and 75% probability of detecting one or more LNs metastases. These data indicate that removing 25 LNs might represent the lowest threshold for the extent of lymphadenectomy at RC. Our findings confirm the importance of an extended lymph node dissection.