Lateral lymph node dissection for lower rectal cancer.

The mainstay of surgical therapy for rectal cancer is colectomy (including lesions) with lymph node dissection. The lymphatic spread of rectal cancer can proceed in two directions: medially toward the origin of the inferior mesenteric artery or laterally toward the pelvis aslong the internal iliac artery. To prevent postoperative recurrence, lymph nodes situated along these two axes should be adequately dissected, leaving no residual cancer cells. In Japan, the standard procedure for advanced lower rectal cancer is mesorectal excision and lateral lymph node dissection with autonomic nerve preservation. In Europe and North America, lateral lymph node dissection used to be performed, but it led to increased blood loss, complications, and dysfunction, with no improvement in survival. Lateral lymph node dissection is thus no longer performed. Instead, multidisciplinary therapy combining mesorectal excision with preoperative chemoradiotherapy is now the standard treatment for advanced rectal cancer. Although lateral lymph node dissection decreases the rate of local recurrence similar to preoperative chemoradiotherapy, whether it contributes to improved survival remains unclear. In addition, it is unlikely that prophylactic lateral lymph node dissection is required in all patients with rectal cancer. Definition of the indications for lateral lymph node dissection is thus an important concern.