Is a limited lymph node dissection an adequate staging procedure for prostate cancer?

Generally lymph node dissection is only considered a staging procedure for prostate cancer. Therefore, the need for meticulous lymph node dissection is often questioned and only sampling is suggested. We performed a prospective study to identify the pattern of lymph node metastasis in prostate cancer and determine how extensive lymph node dissection must be not to under stage cases.

All patients with clinically organ confined prostate cancer, no prior hormonal treatment, negative preoperative staging computerized tomography and bone scan, who underwent radical prostatectomy between 1989 and 1999, were evaluated prospectively as to the number and location of lymph node metastasis. A meticulous lymph node dissection was performed along the external iliac vein, obturator nerve and internal iliac (hypogastric) vessels. Nodes from each location and side were submitted separately for histological evaluation.

In 365 patients with a median serum prostate specific antigen of 11.9 ng./ml. (range 0.4 to 172) the median number of nodes removed was 21 (range 6 to 50). Lymph nodes were positive in 88 (24%) patients and the median number of positive nodes was 2 (range 1 to 19). Internal iliac lymph nodes were positive in 51 (58%) of the 88 patients, including 34 with additional positive lymph nodes along the external iliac vein and/or obturator nerve. Internal iliac lymph nodes alone were positive in 17 (19%) of 88 patients.

There were significant numbers of lymph node metastases at all 3 different areas of lymphadenectomy. Positive lymph nodes were found along the internal iliac artery in more than half (58%) of the patients and exclusively in 19%. Therefore, we consider lymph node dissection along the internal iliac (hypogastric) vessels essential for representative staging. Without this dissection a fifth of node positive cases would have been under staged and diseased nodes would have remained in more than half of the cases.