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.