Anatomical Basis for Pelvic Lymphadenectomy in Prostate Cancer: Results of an Autopsy Study and Implications for the Clinic

Significance of micrometastases in pelvic lymph nodes detected by real-time reverse transcriptase polymerase chain reaction in patients with clinically localized prostate cancer undergoing radical prostatectomy after neoadjuvant hormonal therapy

OBJECTIVE

To clarify the significance of micrometastases in pelvic lymph nodes in patients treated by radical prostatectomy (RP) for prostate cancer after neoadjuvant hormonal therapy (NHT).

PATIENTS AND METHODS

The study included 52 patients with clinically localized prostate cancer who received NHT followed by RP. The expression of prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) in 989 lymph nodes isolated from the 52 patients were assessed by a fully quantitative real-time reverse-transcriptase polymerase chain reaction (RT-PCR). We regarded specimens in which either PSA or PSMA mRNA were positive as showing the 'presence of micrometastasis'. Lymph node specimens were also stained immunohistochemically with an antibody against PSA.

RESULTS

Pathological examinations detected tumour cells in 11 lymph nodes from four patients, and real-time RT-PCR further identified micrometastasis in 40 lymph nodes from 19 patients with no pathological evidence of nodal involvement. The presence of micrometastatic cancer cells was confirmed by immunohistochemical staining in 19 lymph nodes from 11 patients with pathologically negative nodes. The presence of micrometastases was significantly associated with other conventional prognostic variables, including the pretreatment serum PSA level, biopsy Gleason score and surgical margin status. The biochemical recurrence-free survival rate in patients with no micrometastasis was significantly higher than that in those with micrometastasis. Furthermore, multivariate analysis identified the presence of micrometastasis as an independent factor predicting biochemical recurrence.

CONCLUSIONS

Although residual foci of atrophic prostate cancer cells in resected lymph nodes after NHT can be difficult to diagnose by routine pathological examination, the present results show the usefulness of quantitative real-time RT-PCR targeting PSA and PSMA genes for detecting micrometastatic tumour foci in pelvic lymph nodes from patients with localized prostate cancer treated by NHT followed by RP. Furthermore, the present findings suggest that micrometastases in pelvic lymph nodes might be, at least partly, important in the development of biochemical recurrence in some patients undergoing RP after NHT.

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.