Total mesenteric excision in the treatment of rectal carcinoma: methods and outcomes

Abstract

The American Cancer Society estimates that there are approximately 40,000 new cases of rectal cancer in the United States per year, representing 30% of all colorectal cancers.Of these, approximately three-fourths will undergo resection with the intent to cure with a 5-year local recurrence rate of 8.5%, 16.3%, and 28.6% for stage pT1, pT2, and pT3 rectal cancer, respectively [1]. Overall 5-year survival data are only 22–26% for pT3 disease [2–5]. Like colon cancer, the majority of rectal cancers are adenocarcinoma.Achieving adequate resection margins in rectal cancer is more difficult due to the anatomic location of the rectum in the pelvis.Whereas wide margins of resection can be obtained in colon cancer by mobilization of the mesentery, rectal cancer is anchored by the non-mobile mesorectum to the bony pelvis and is closely surrounded by somatic structures such as the hypogastric nerve plexus, the prostate and seminal vesicles in men, and the uterus and vagina in women. The inability to remove tissue en bloc in rectal cancer excision leads to a three-fold more common local recurrence rate for rectal cancer compared to colon cancer [6]. Fortunately rectal adenocarcinomas are well suited for cure by resection based on several of their inherent characteristics.The majority have histologic criteria favorable for resection and rarely does intramural spread occur further than a centimeter from its palpable margin [7].The metastatic routes of rectal cancer are usually limited to the draining lymph nodes and liver.In one study, o5% of patients had distal bone, pulmonary, or cerebral metastase [7].In many ways, rectal cancer behaves as a local rather than a systemic disorder, which makes it more readily cured by surgical methods. The boundaries of the margin of resection that will optimally reduce local recurrence rates, increase patient survival, and minimize co-morbidities are currently debated.The aim of this article is to review the technique of total mesenteric excision (TME) used in conjunction with low anterior resection (LAR) and abdominoperineal resection (APR) of rectal adenocarcinomas.Analysis of the routes of rectal cancer spread will be used to rationalize choices of adequate boundaries of resection to optimize outcomes (i.e. should the lateral borders include the entire mesorectum, what constitutes an adequate distal margin, and how proximal should the lymphovascular structures be divided). Favorable outcomes not only reflect cure of disease and prevention of recurrent disease, but also take into account the prevention of undesired co-morbidities such as anastomotic leaks, compromise of sphincter function, loss of bowel control, and the impairment of bladder and sexual function.