Optimal lymph node dissection for T3-T4 lower rectal cancer, the so-called "high risk" group: the Japanese experience.

The principal aim of radical surgery for rectal cancer is complete resection of the tumor together with its feeding and lymphatic vessels. There are two types of lymphatic flow from lower rectal cancer: proximal lymphatic flow, toward the root of the inferior mesenteric artery in the mesorectum, and lymphatic flow toward the pelvic sidewall alongside the internal iliac blood vessels beyond the mesorectum. In order to prevent postoperative local recurrence after resection of rectal cancer, it is important to fully excise all lymphatic tissue around the rectum, leaving no remnants of cancer cells. In the West, the primary goal of rectal surgery is complete resection with free circumferential and distal surgical margins: total mesorectal excision (TME) or tumor-specific mesorectal excision (TSME). T3-T4 lower rectal cancers with full thickness penetration of the rectal wall frequently show regional mesorectal lymph node metastasis and, sometimes, extramesorectal invasion or lateral pelvic node metastasis. Therefore, in the West, patients with T3-T4 lower rectal cancer, the so-called “high risk” group, are typically treated by TME in combination with radiotherapy and chemotherapy. In Japan, on the other hand, surgeons typically carry out extended TME/TSME combined with pelvic side wall node dissection (PSD) in such “high risk” group patients. The pelvis presents certain anatomical difficulties from the surgical point of view associated with various complications such as bleeding and impotence. However, despite these difficulties, Japanese surgeons have managed to successfully carry out extended node dissection for many years, with the first PSD procedure for rectal cancer being reported by the Japanese surgeon Dr. Kuru in 1940. Unfortunately, this report is only available in Japanese. Good oncological outcomes may be obtained by optimal dissection techniques. Recently, the incidence of local recurrence of T3-T4 lower rectal cancer after resection has been shown to be 10% or lower in Japan, even when performed without adjuvant radiotherapy. However, important issues remain to be discussed with regard to PSD. While extended node dissection has been found to decrease local recurrence, injury to the autonomic nervous system may sometimes occur. We found that PSD frequently resulted in urinary and sexual dysfunction due to such injury. Furthermore, PSD has been criticized based on the lengthy operation time required and amount of bleeding incurred. In this report, I would like to describe the current state of knowledge with regard to lymph node metastasis from rectal cancer (site, frequency and clinical impact) based on our experience in Japan. In particular, I would like to discuss PSD with reference to the data accumulated in the Japanese Colorectal Cancer Group study “Research on pelvic side wall dissection”, which was conducted in order to clarify the risk profile for, and clinical impact of, PSD together with the incidence of side wall node metastasis and rates of survival and local recurrence (1). G Chir Vol. 30 n. 10 pp. 393-399 Ottobre 2009