The ideal treatment for rectal cancer should maximize sphincter preservation and lead to optimal oncologic outcomes characterized by low morbidity and mortality. In this study, the oncologic outcomes after a TSME of rectal cancer showed a 77.5% 5-year cancer-specific survival rate, a 9.2% local recurrence rate, and a 21.1% systemic recurrence rate.
For the past 20 years, the results of treatment for rectal cancer have improved in terms of local recurrence and cancer-specific survival rates due to adjuvant chemoradiotherapy and optimized surgical techniques. The TME has reduced the local recurrence rate from 20 to 30% [
1,
2] to 5 to 7% [
11,
12]. Adjuvant chemoradiotherapy after a curative resection of rectal cancer reduced the local recurrence rate from 24 to 11% in the GITSG study and from 25 to 16% in the NSABP R-01 study [
3,
4]. In 1990, these two randomized trials prompted a National Cancer Institute Consensus Conference in the USA to recommend postoperative adjuvant chemoradiotherapy for patients with T3-stage rectal cancer, involvement of lymph nodes, or both [
5]. However, efforts to optimize the surgical technique led to the TME being changed to the TSME because the TME had a high morbidity associated with an anastomotic leakage rate of 23.5% [
7-
10,
13]. In the TSME, a TME is performed for middle and distal rectal cancer, and a partial mesorectal excision with sharp pelvic dissection is performed for proximal rectal cancer. The TSME has been associated with a local recurrence rate of 9.2% at our institution, which is comparable to another TSME study, with a rate of 9.7%, reported by Law and Chu [
13], but unfavorable compared with the 5.4% rate reported by Kim et al. [
14]. This difference seems to be due to the application of adjuvant chemoradiotherapy, which was performed in all patients with postoperative pathologic stages exceeding II in the study of Kim et al. [
14], but was not routinely performed for patients in the study of Law and Chu [
13]; in the latter series, adjuvant chemoradiotherapy was performed only when local clearance was in doubt. In the present study, we did not perform adjuvant chemoradiotherapy in any patient with a tumor stage exceeding stage II; rather, we used it almost postoperatively in selective patients with multiple lymph-node invasion, lymphovascular invasion, or suspected positive resection margins. Thus, the slightly high rate of local recurrence seemed to be caused by not routinely administering adjuvant chemoradiotherapy after the TSME. Therefore, the use of adjuvant chemoradiotherapy in all patients with tumor stages exceeding stage II would be helpful to improve the local recurrence rate after a TSME. In 2004, the German Rectal Cancer Trial [
15] compared the applications of preoperative and postoperative chemoradiotherapy, and reported a 13% 5-year local recurrence rate after postoperative treatment and a 6% rate after preoperative treatment. Thus, in 2009, the National Comprehensive Cancer Network guidelines designated preoperative chemoradiotherapy as a standard therapy in clinical stage II/III patients with suspected lymph-node invasion and cT3 stage [
16]. In the present study, we found that pN stage, positive distal resection margin, and positive circumferential resection margin were independent risk factors for local recurrence. These factors are similar to those of other TME studies [
13,
17-
19], so if these risk factors are predicted in the preoperative magnetic resonance image or TRUS, more aggressive NCRT should be performed with the TSME. However, for effective use of NCRT, more accurate diagnostic tools are needed for predicting risk factors, which include positive lymph nodes, circumferential resection involvement, and anal sphincter involvement, because a patient with a lower stage than expected or with no risk factors could be over-treated. Also, predictive factors for response to NCRT should be developed because patients with disease during NCRT would be treated by using a useless method. Kim et al. [
14] suggested that preoperative chemoradiotherapy would be better in patients with rectal cancer localized in the distal rectum and in high-risk patients such as those with a positive circumferential resection margin and invasion of the anal sphincter. Until more accurate diagnostic tools and predictive factors for response to NCRT are developed, the suggestion of Kim et al. [
14] could provide good selective indications for effective use of NCRT.
The rates of systemic recurrence have been reported to be 16.3 to 22.1%, which are similar to our present results [
14,
20-
22]. Known risk factors for systemic recurrence include sex, tumor stage, circumferential resection margin, and preoperative serum CEA level [
14,
17,
22]. In the present study, the multivariate analysis revealed that the risk factors for systemic recurrence were pN stage and preoperative serum CEA level. Systemic adjuvant chemotherapy should also be considered when these factors are detected, and more effective regimens, such as the adjuvant chemotherapeutic regimens for colon cancer should be tried.
Our analysis of 782 cases of rectal cancer with pathologic stage I to III cancer after a TSME found a 5-year cancer-specific survival rate of 77.5%, a local recurrence rate of 9.2%, and a systemic recurrence rate of 21.1%. The risk factors affecting the cancer-specific survival rate were pT stage, pN stage, positive distal resection margin, and positive circumferential resection margin. The risk factors affecting local recurrence were pN stage, positive distal resection margin, and positive circumferential resection margin. The risk factors affecting systemic recurrence were pN stage and preoperative CEA level.
In conclusion, the oncologic outcomes at our institution after a TSME for patients with resectable rectal cancer were similar to those reported in other recent studies, and we established the risk factors that could be crucial for the planning of treatment and follow-up.