Adenocarcinoma of the rectum remains a significant public health challenge, with 39,000 new cases predicted for 1998 resulting in an estimated 8,500 deaths. The current standard therapy for invasive adenocarcinoma of the rectum is radical en bloc resection with negative surgical and histologic margins. Lesions of the mid- and proximal rectum may, in most instances, be treated with low anterior resection, with appropriate distal margins and preservation of sphincter function.
In contrast, lesions of the distal rectum often do not allow the surgeon and patient the option of a sphincter-preserving procedure, as the requirement for an adequate distal margin mandates an abdominoperineal resection. This therapeutic approach necessitates formation of a permanent colostomy, which is associated with compromised quality of life for a significant percentage of patients. Abdominoperineal resection is also associated with significant morbidity, which includes urinary dysfunction in 10% to 70% (average 30%) of patients and male sexual dysfunction; specifically, impotence and retrograde ejaculation occur in 15% to 100% and 3% to 39% of patients, respectively.[3-7] The mortality of abdominoperineal resection ranges from 1% to 5%[8-12] and has been reported to be significantly increased in patients over 70 years of age.
For these reasons, alternatives to abdominoperineal resection, both surgical and nonsurgical, have been sought. Nonsurgical modalities include endocavitary radiation, an approach extensively utilized by Papillon, who reported a 5-year survival rate of 72% and a local recurrence rate of 7% in selected patients so treated.[13-15] Electrofulguration has also been utilized for both palliation of advanced-stage disease and cure of early-stage lesions in patients judged to be at prohibitive risk of complications and death from radical surgery. Multiple authors have reported survival rates of 52% to 68% in patients followed for a minimum of 4 years after electrofulguration therapy.[16-19] Laser therapy is employed as a palliative modality to maintain rectal lumen patency, sparing high-risk, advanced-disease patients the need for colostomy diversion.[20,21] Nonsurgical therapeutic approaches to rectal cancer do not allow for pathologic and histologic evaluation of a completely resected specimen and, therefore, provide limited staging information.
This article will focus on sphincter-sparing surgical modalities for distal rectal cancer. An extensive review of the literature pertaining to local excision alone, local excision plus postoperative radiation therapy (with or without chemotherapy), and local excision following preoperative chemoradiotherapy will be presented. The literature on this subject is dominated by single-institution, retrospective reports. However, we feel that this represents a valuable collective experience worthy of review. These reports provide a foundation on which future multicenter, prospective trials designed to clarify the role of sphincter-preserving surgery for invasive distal rectal cancer can be based. The design and preliminary results from the sole multi-institution prospective trial of local excision and postoperative chemoradiotherapy, Cancer and Leukemia Group B (CALGB) trial 8984, will also be reviewed. These collective results indicate that the optimal strategies for local excision and sphincter-preserving therapy require further study.
Additional topics discussed in this review include assessment of risk of lymph node metastases, the role of salvage radical surgery following local recurrence, and quality of life following local excision for invasive distal rectal cancer.
Local excision for invasive distal rectal adenocarcinoma was initially utilized in patients considered too ill to undergo abdominoperineal resection. Follow-up of these patients indicated that they did not sustain inordinately high rates of local recurrence or death from metastatic disease when compared to historical outcome data for abdominoperineal resection.[13,23-28]
Attempts to apply local excision-based therapy to rectal cancer in patients who are candidates for radical surgery demand that the results be compared to those of current standard therapy. Although the morbidity and quality-of-life issues associated with abdominoperineal resection and, to a lesser extent, low anterior resection are significant, these procedures remain the standard of care. The criteria by which the treatment of rectal adenocarcinoma must be judged remains the frequency of local disease recurrence, disease-free survival, and overall survival.
Several recent series review these parameters in patients treated for early-stage invasive rectal adenocarcinoma with either abdominoperineal resection or low anterior resection. The Dukes staging system, Astler-Coller modification of the Dukes system, and the TNM staging system are all represented in the articles discussed in this review. In order to assist the reader, each of these staging systems is outlined in Table 1.
Sticca et al (Table 2) reviewed the recurrence patterns and outcomes of 71 patients with stage I rectal adenocarcinoma treated with radical resection at a single institution. Of the 71 patients, 20 had T1 N0 M0 cancers and 51 had T2 N0 M0 cancers. The median follow-up for all patients was 81 months. The median number of lymph nodes examined per specimen was 32.
There were no recurrences in the 20 patients with T1 lesions. All seven recurrences (10%) occurred in patients with T2 lesions. Two of the recurrences were local only. Four patients recurred with distant disease, and one recurred with local and distant disease during follow-up.
In the T2 group, the 5- and 10- year disease-free survival rates were 88% and 83%, respectively. Of interest is the fact that the T1 group included one patient with lymphatic and/or vascular invasion and the T2 group included four such patients. Only one of the five patients with these histologic characteristics suffered a recurrence. This observation will be reconsidered later in this review, when the factors associated with recurrent disease following local excision are discussed.
Wilson and Beahrs assessed 5- and 10-year survival in 556 patients with mid- and proximal rectal cancers treated with low anterior resection, and reported 89% and 86% rates of 5-year survival for patients with Dukes A (T1), and Dukes B1 (T2) lesions, respectively (Table 2). Grigg et al reported on 268 patients with carcinoma of the rectum confined to the submucosa (T1) treated with either abdominoperineal resection or low anterior resection; the 5-year cancer specific survival rate in these patients was 88% (Table 2).
McDermott et al studied 276 patients with Dukes stage A lesions of the distal rectum treated with abdominoperineal resection; the local recurrence rate in these patients was 10% (Table 2). In the series of McDermott et al, local recurrence doubled in patients with poorly differentiated lesions, as compared with patients with moderate- or well-differentiated lesions. Median survival was 35 months following local recurrence alone and 39 months following distant recurrence. Overall survival was not reported.
Willet et al evaluated patients with stage I rectal cancer treated with abdominoperineal resection. They reported no treatment failures among 12 patients with T1 lesions, whereas 8 (15%) of 52 patients with T2 lesions did develop a recurrence. Risk factors associated with recurrent disease, in addition to muscularis propria invasion (T2 lesions), included vascular/lymph vessel involvement and the presence of extensive stromal fibrosis on histologic evaluation.
In a review of a 25-year experience at St. Marks Hospital, London, Dukes and Bussey reported outcome results for 3,596 rectal cancer patients (Table 2). The corrected cancer-specific 5-year survival rate for Dukes A and B lesions (T1-3 N0) was 82.5%. The corrected 5-year survival rate for lesions confined to the bowel wall, Dukes A (T1-2), was 97.7%. The percentage of lymphatic metastases was 14.2% in patients whose cancer was confined to the bowel wall (T1-T2). Among patients with "slight spread" (ie, minimal invasion into extrarectal tissues; T3), the percentage of patients with positive lymph nodes was 43.2%, based on an evaluation of 516 cases.
Taken as a group (Table 2), the 5-year survival rates for T1 lesions from the two larger series that included poorly differentiated cancers[30,31] are comparable, at 89% and 88%, respectively. None of the 20 patients with T1 tumors in the series of Sticca et al, all of whom were alive at 5 years, had poorly differentiated lesions. The observations of McDermott et al and Wilson et al of a 10% local recurrence rate and a 6% anastomotic recurrence rate, respectively, should be kept in mind as we review the sphincter-preserving surgical modalities, with and without various adjuvant treatment modalities, for invasive adenocarcinoma of the rectum.