Sharp Mesorectal Excision Is Now Recommended for All Rectal Cancers

LEXINGTON, Kentucky—Inadequate surgical resection is emerging as a major cause of recurrence in rectal cancer, and most such recurrences could be prevented by use of sharp mesorectal excision (SME) rather than blunt dissection, according to Alfred M. Cohen, MD. Dr. Cohen, director of the Lucille P. Markey Cancer Center at the University of Kentucky in Lexington, reviewed state-of-the-art rectal cancer surgery.

"Since rectal cancer surgery is a local-regional therapy, its efficacy is based principally on its rate of local control," Dr. Cohen said. "The pelvis is a common site of recurrence, which is a major cause of morbidity and death. Pain due to nerve invasion, perineal breakdown, and obstruction, plus bleeding and fistulization, often creates an unmanageable problem. Salvage therapy is of limited and usually temporary efficacy, so everything possible must be done to prevent recurrence."

Conventional "blunt" dissections leave positive lateral margins in 25% of patients, and Dr. Cohen said that about 80% of such patients develop recurrences. Local recurrence rates vary from 10% to 50% depending on the surgeon, which suggests that surgical technique is an important risk factor.

"Where circumferential margins are clean to 0 to 1 mm, the local recurrence rate is 25%. Where margins are clean for better than 1 mm, the local recurrence rate drops to 3%. High-quality surgery changes the benchmark for adjuvant therapy," Dr. Cohen said. "

Removing Entire Mesentery

"The fascial covering over the rectum explains why even with only a 1 mm clean margin we can cure the patient," Dr. Cohen said. He explained that the best way to obtain a clean circumferential margin is by "sharp" total mesorectal excision (TME). This involves removal of the entire rectal mesentery, including that distal to the tumor, as an intact unit (see Figure 1). "Most rectal cancers through the wall are confined to fatty tissue surrounding the cancer, and nodal spread in half of patients is distal to the rectum, toward the anus," Dr. Cohen explained.

TME requires dissection in an areolar pane outside the visceral fascia enveloping the rectum. "In contrast to conventional blunt dissection techniques, the envelope encompassing the pelvic tissue is removed intact, without the risk of mesorectal or rectal perforation frequently associated with blunt dissection along the rectosacral fascia. This maximizes the likelihood that the lateral or peripheral margin will be negative and facilitates nerve preservation," Dr. Cohen said. "We must do everything we can to prevent the need for colostomy, avoid a poorly functioning neorectum, and preserve sexual function." He said that the key to good results is the use of sharp mesorectal excision, including cautery and scissor dissection in the well-defined plane outside the mesorectal visceral fascial lining.

Randomized Trials Awaited

Randomized trials of TME have not yet been done, but Dr. Cohen said that a 5-year prospective study in Sweden reported 7% local recurrences with TME compared to a historical rate of 23% with blunt dissection.

Since 80% of rectal cancer patients are treated at community hospitals, that setting must be the focus of initiatives to encourage the use of TME. Dr. Cohen said that the American College of Surgeons oncology group has put together a program to train surgeons in this technique, with the aim of eventually enabling most community hospitals to have at least one surgeon extensively trained in TME.