Is a limited lymphadenectomy targeting obturator nodes alone an adequate procedure for Japanese men undergoing radical prostatectomy?

BACKGROUND: The objective of the present study was to investigate the significance of pelvic lymphadenectomy during radical prostatectomy in Japanese men with prostate cancer. METHODS: A total of 178 consecutive patients who underwent radical prostatectomy and standard pelvic lymphadenectomy targeting the external iliac nodes and obturator fossa for clinically localized prostate cancer were studied. The median observation period of this series was 18 months (range: 3-36 months). RESULTS: Lymph node metastases were detected in 13 patients; that is, positive nodes were located in the external iliac nodes alone in seven patients, the obturator fossa alone in four patients, and both external iliac nodes and obturator fossa in two patients. Of these 13 patients, all of the seven with more than one positive node demonstrated biochemical recurrence, whereas five of the six with single node involvement remained without signs of biochemical recurrence. Furthermore, a single positive node was located in the external iliac region in five of the six patients. When a group at high-risk for lymph node metastasis was defined as those meeting more than two of the following three criteria: (i) pretreatment serum prostate specific antigen value > or = 20 ng/mL; (ii) biopsy Gleason sum > or = 8; or (iii) percentage of positive biopsy core > or = 50%, the incidence of lymph node metastasis was 24.5% in the high-risk group and 0.8% in the low-risk group. CONCLUSIONS: These findings suggest that limited dissection of the obturator node alone may not be sufficient for Japanese men undergoing radical prostatectomy; therefore, we recommend performing standard pelvic lymphadenectomy targeting both the external iliac nodes and the obturator fossa for patients at high-risk of lymph node involvement.