LEXINGTON, KentuckyInadequate 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
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
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.