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Prospective mapping of lymph node metastasis in Japanese patients undergoing radical cystectomy for bladder cancer: characteristics of micrometastasis.

OBJECTIVE
To investigate node-disease prevalence including micrometastases and its survival impact on bladder cancer patients.


METHODS
A total of 60 patients participated in this study, in which extended lymph node dissection was carried out according to the prospective rule (below aortic bifurcation). Radical cystectomy and extended lymph node dissection were performed by open surgery (n = 23) or laparoscopically (n = 37). Perioperative, pathological and follow-up data were collected. Micrometastasis in lymph nodes was investigated by pan-cytokeratin immunohistochemistry. Recurrence-free survival was estimated with the Kaplan-Meier method.


RESULTS
The median number of lymph nodes removed was 29 (range: 10-103) and there was no significant difference between the two groups (open group: median 30, laparoscopic group: median 29). Routine pathological examination revealed that 10 patients had lymph node metastases. Immunohistochemistry revealed micrometastases in four additional patients (pNmicro+), who had been diagnosed with pN0 on routine pathological examination. After excluding the three patients with pure nonurothelial carcinoma on the final pathology (small cell carcinoma: n = 2, adenocarcinoma: n = 1), 10 out of the 57 urothelial carcinoma patients (17.5%) had node metastasis, and an additional 4 out of the 47 pN0 patients (4/47, 8.5%) had micrometastasis. The 2-year recurrence-free survival rates divided by pN stage were 82.4% for pN0, 66.7% for pNmicro+ and 12.5% for pN+ (three-sample log-rank test, P < 0.0001). Three out of the four patients with pNmicro+ were disease free at the last follow-up.


CONCLUSIONS
We confirmed under extended lymph node dissection that a substantial proportion of the patients had node metastasis (pN+: n = 10 and pNmicro+: n = 4), and the pN stage influenced patient survival. Our observations of micrometastasis yielded additional evidence for the potential survival benefit of extended lymphadenectomy by eliminating microdisease.