Sphincter-Preserving Operations for Rectal Cancer
Sphincter-Preserving Operations for Rectal Cancer
Dr. Enker offers an orderly presentation of many of the factors related to sphincter-preserving operations, quality of life, and outcome in the surgical management of the patient with rectal cancer. From the practical perspective of a very experienced surgeon, he provides broad guidelines for sphincter-conservation surgery that both the surgeon and nonsurgeon should find useful.
Enker properly defines the treatment goal in rectal cancer as the achievement of the widest application of surgical sphincter preservation possible while avoiding local recurrence, and he offers reliable methods for accomplishing this goal. The thesis that new techniques, improved understanding, and multimodality therapy have made safe and effective sphincter-preserving surgery more attainable than ever before is directly to the point. A number of issues, nevertheless, deserve comment.
Enker gives particular emphasis to the benefit of total mesorectal excision, a term coined by Heald to describe the complete removal of lymph-bearing extrarectal tissue lying central to the endopelvic fascia. It has been my understanding that a properly performed total or near-total radical rectal resection has always included removal of this tissue, leaving the pelvic side walls bare. Heald offered the unique addition that once the dissection proceeded distally to the levator ani muscle along the pelvic side wall, it would then continue centrally along the muscular coat of the rectum and advance proximally to skeletonize the rectum to the desired level.
Heald's data, as well as those of Enker, show an impressively low incidence of local recurrence. One criticism of the Heald experience, however, is that 18% of the operative group were excluded from analysis because gross cancer was transected. Obviously, exclusion criteria of this type must be known for accurate interpretation of data. Cancers fixed to the pelvic side wall in which positive circumferential margins inevitably lead to local failure are precisely those that benefit the most from high-dose preoperative irradiation. By potentially sterilizing the peripheral margins, irradiation converts the fixed cancer to curative resectability. In our two-decade experience using high-dose preoperative irradiation and sphincter-preserving surgery, no patient, despite fixation, was excluded from analysis because the tumor was transected. Of over 300 patients, only 3 were deemed inoperable following irradiation.
Need for Standardized Nomenclature Seconded
I would join Dr. Enker in his passionate plea for the standardization of nomenclature to enable proper data comparison. The main points of contention are: (1) where is the distal limit of the rectum, and (2) what should be used as the logical reference point in measuring the level (height) of the inferior margin of the rectal cancer?
The time-honored use of the anal verge as the reference point no longer makes sense. The lymphatic watersheds for rectal cancer spread are the levator ani muscle and the anorectal ring, which is the true limit of the rectum as defined in anatomic texts. Furthermore, for practical purposes, the anorectal ring is the lowest limit of anastomosis. Cancers that arise in the anal canal are not cancers of the rectum. The margin distal to the resected cancer does not include any portion of the anal canal, except for the margin after an abdominoperineal resection. For all these reasons, surgeons should consider the rectum to end at the anorectal ring, and this should be the point of reference for measuring the level (height) of the interior margin of the cancer.
The genesis of using the anal verge as the standard comes from the archaic tradition of utilizing the ruled markings on the exterior of the rigid sigmoidoscope. These markings could be read directly by the examiner. This was acceptable when sphincter-preserving options for distal rectal cancer were not a consideration. In this period of enlightenment, when distal margins can be minimized by the use of high-dose preoperative radiation and coloanal anastomosis is employed, precise measurements related to the anorectal ring have become critical. The measurements can be determined by digitally pacing off each centimeter to the anorectal ring distal from the intramural component of the cancer. In patients with a deep perineum, where digital penetration is difficult, that distance can be easily measured with the tip of the rigid sigmoidoscope with the cancer under view.
I have strong concerns regarding the use of anterior resection for the nonirradiated rectal cancer arising in the distal 3 cm of the rectum, particularly in the male patient. The recommended application of an isolating clamp and tumoricidal irrigation of the rectum distal to the cancer may be difficult or impossible in these low-level cancers. These problems related to cancers in the distal 3 cm of the rectum provide a convincing argument for utilizing preoperative irradiation and initiating the dissection transanally. By using this approach, endoluminal viable tumor cells may be avoided, and one can ensure the adequacy of the margin distal to the cancer.
Preop Radiation Broadens Use of Sphincter-Preserving Surgery
Dr. Mohammed Mohiuddin and I have collaborated to define selection criteria for the use of preoperative external irradiation to broaden the use of sphincter-preserving operations. All cancers in the distal 6 cm of the rectum and any unfavorable cancers (T3, N+) are irradiated with 5,580 cGy in 180-cGy fractions. All rectal cancers, except those in the distal 3 cm of the rectum that remain fixed after irradiation, are treated by sphincter-preserving surgery.
In an effort to ensure the maximum margin distal to the cancer, we have developed an operation to achieve sphincter preservation for cancers in the distal 3 cm of the rectum. In this procedure, dissection is begun at or immediately superior to the pectinate line with full-thickness mobilization of the rectum for a distance of 10 to 12 cm. Following this, during the abdominal phase, radical total proctectomy and resection of the sigmoid colon are accomplished. A direct hand-sewn anastomosis between the descending colon and the anal canal is performed transanally.
We have used this technique in over 100 patients with cancers in the distal 3 cm of the rectum. The 5-year Kaplan-Meier actuarial survival rate is 85%, and the local recurrence rate is 9%. The lowest level treated in this manner was 5 mm, and in 19 patients with tumors at a level of 1 cm or less, there were only two (11%) recurrences. There was no local recurrence when the postirradiated tumor in the distal 3 cm was limited to the rectal wall, even in the presence of nodal disease.
As part of our program, we have also utilized full-thickness local excision for the postirradiated rectal cancer. In 57 patients treated in this manner, the local recurrence rate was 15%, and the 5-year Kaplan-Meier actuarial survival rate was 87% for those who underwent elective surgery.
The Ideal Contemporary Approach
In this excellent presentation, Dr. Enker has done much to keep us mindful of the need for and methods to appropriately apply selective sphincter- preserving operations. Dr. Enker said it best when he suggested that preoperative irradiation and total mesorectal excision may be the ideal contemporary approach to extending the limits of sphincter-preservation surgery for rectal cancer.