Predicting Lymph Node Metastasis in Patients with Advanced Rectal Cancer: A Prospective Study for the Characteristics of Lymph Node Metastasis of Mesorectum and Extra-Mesorectum

ABSTRACT

It is very important to tallow that pelvic lymphadenectomy associated with proctectomy must be based on the principle of oncologic surgery and encompass all predictable pathways of extension of rectal cancer for curative surgical resection. We investigated the characteristis of lymph node metastasis in patients with rectal cancer prospectively. 108 consecutive patients with rectal cancer underwent curative surgical resection were enrolled in this study. Rectal cancers were divided into two groups, upper and mid-lower. Upper rectal cancer was defined as the tumor above the peritoneal reflexion. Lymph nodes were stratified as mesorectum, distal mesorectum (defined as distal part more than 2 cm from the lower margin of the tumor), intemal iliac, common iliac, presacral, superior rectal artery, inferior mesenteric artery, paraaortic lymph node. Average number of sampled nodes in these groups 18.5+/-10.7, 3.6+/-3, 2.3+/-3, 1.8+/-1.3, 4 +/-4.1, 1.6+/-2, 3.1+/-3.2, 5.4+/-4.7 respectively. 60 of all patients showed positive lymph node. The over all percentages of patients with positive lymph node was 53% in mesorectum, 12% in distal mesorectum, 8% in intemal iliac, 4.5% in common iliac, 4.5% in presacral, 10% in superior rectal artery, 6.5% in inferior mesenteric artery, 4% in paraaortic lymph node. The over all percentages of patients with positive lymph nodes in each group were 60% (27/45), 9% (4/45), 6.5% (3/45),2% (1/45), 2% (1/45), 13% (6/45), 11% (5/45), 1% (1/45) respectively in upper rectal cancer, 49% (31/63), 14% (9/63), 9.5% (6/63), 6% (4/63), 6% (4/63), 8% (5/63),3% (2/63),5% (3/63) respectively in mid-lower rectal cancer. There were skip metastasis in 3 patients with upper rectal cancer, 2 patients with mid-lower rectal cancer. Age, depth of invasion, tumor size, tumor differentiation among clinicopathologic factors were predictive factors of lymph node metastasis to mesorectum. Risk factors of metastasis to extra-mesorectal lymph node were younger age (5.0 cm), involved circimferential (>50%), and positive CA 19-9 (>37 U/ml). These results suggest that more careful upward lymphadenectomy must be carried out especially in upper rectal cancer and also careful lateral dissection in selected patients and more generous excision of distal mesorectum especially in mid-lower rectal cancer is needed for curative resection according to clinicopathologic factors.