ORLANDO, FlaSharp dissection through a plane between the visceral and parietal layers of the pelvic fascia permits a clean removal of the entire rectum and mesorectum, and greatly decreases local recurrence of rectal cancer, Warren E. Enker, MD, reported at the 52nd Annual Cancer Symposium of the Society of Surgical Oncology (SSO). Typically, he said, patients have been treated with blunt dissection, resulting in inadequate mesorectal excision.
Dr. Enker, vice chairman of surgery, Beth Israel Medical Center, New York, reported data on 545 patients treated with sharp dissection for total mesorectal excision (TME). These patients had a 5-year survival rate of 74%, local recurrence rate of 5%, and local recurrence rate of 10% or greater only in patients with T3, N2 or T4 disease.
He said that, in contrast, about 25% of blunt dissections leave positive lateral circumferential margins, which are associated with an 80% local recurrence rate. Additional advantages of Dr. Enkers approach are that it permits autonomic nerve preservation and sphincter preservation in most cases.
Dr. Enker attributes the high local recurrence rate with blunt dissection partly to the presence of the rectosacral ligament. In the typical blunt dissection, the surgeons hand slides down, meets resistance at the ligament, and tends to go forward into the mesorectum, which is proximal to the location of most tumors, he said. This violates the mesorectum and leaves lymph nodes containing cancer attached to the sacrum.
The accepted treatment for advanced rectal cancer is to resect all regional disease and leave negative circumferential margins. The concept is similar to the concentric circles of a target, he said.
The center is the rectum, the portion of the large bowel that is in the true pelvis from the sacral promontory to the levators. Surrounding the lumen is the wall, where there might be a primary tumor. Surrounding that is the perirectal fat, which contains the lymph nodes. Next is the visceral layer of the pelvic fascia, then the parietal layer of the pelvic fascia (see Figure 1). Between these two is an essentially avascular plane which is available for sharp dissection, he said.
The key to Dr. Enkers method of total mesorectal excision is sharp excision along the anatomical plane between the visceral and parietal layers of the fascia. This also permits preservation of the autonomic nerves via careful division of the lateral ligament medial to the pelvic autonomic nerve plexus.
Dr. Enker defined TME as follows: Complete mobilization of the rectum from the sacral promontory to the pelvic floor for cancers within 12 cm of the anal origin and an en bloc resection of the rectum and mesorectum with a 5 to 6 cm mesorectal margin distal to the lowest edge of the primary tumor.
When sharp dissection is used, the visceral layer of the pelvic fascia comes off as an intact layer attached to the meso-rectum, Dr. Enker said. The result is a specimen with a characteristically shining, smooth surface. In correctly resected specimens, the visceral pelvic fascia layer is smooth. Dr. Enker said that, in contrast, specimens removed by blunt dissection often have a gouged appearance.
Sharp dissection also permits a simple approach to quality assurance via the basic color photo of the dissected specimen (Figure 2). The smoothness tells you it is a correctly dissected TME specimen, Dr. Enker said. He also suggested that color photos of excised specimens be used as a component of quality assurance in clinical trials of adjuvant therapy.
Dr. Enker described a study in 246 patients with Dukes B or C rectal cancer treated with TME. There were local recurrences in 3% of Dukes B patients and in 6% of those with positive nodes. In related work, a single-surgeon series reported 5% to 7% local recurrence and 69% survival. A large multiple-surgeon series of 1,400 patients in Europe compared TME with conventional blunt dissection. Five-year survival was 69% for TME vs 42% for blunt dissection, and local failure rates were 8% vs 40%.
Dr. Enker said that the additional time required for sharp dissection will be more than offset by major cost savings due to the decrease in local recurrences. In a cost of illness study, he calculated that TME costs $12,000 to $25,000 less per patient (from diagnosis to death) than conventional resection. At a conservative estimate of 35,000 patients per year, this would save a cool half-billion dollars per year, he said.
Controversies that remain about TME include how to define its use in high rectal tumors, problems with anastomosis dehiscence (occurring in 2.9% of cases), retaining bowel and sexual function, optimal sequencing of adjuvant therapy, and indications for adjuvant therapy.