Sphincter-Sparing Rectal Cancer Surgery Shows Acceptable Local Recurrence Rates

A nationwide Japanese cohort study of 224 patients with very low rectal cancer has found that a technically demanding, sphincter-preserving operation combining transanal total mesorectal excision (TaTME) with intersphincteric resection (ISR) achieved a 3-year local recurrence rate of 7.3 percent, with a 95 percent confidence interval of 4.5 to 11.7 percent. The retrospective multicenter study, conducted across 26 member institutions of the Japan Society of Laparoscopic Colorectal Surgery between January 2012 and December 2019, is described by its investigators as the largest nationwide dataset specifically examining oncological outcomes of TaTME combined with ISR in Japan. The work extends the earlier Ta-Ta-Mi analysis, which followed 706 TaTME patients at 26 institutions and reported a 3-year cumulative local recurrence rate of 6.82 percent, by narrowing the focus to patients whose tumors sat within 5 centimeters of the anal verge and who underwent the combined procedure.

The combined operation addresses one of the hardest problems in rectal cancer surgery: removing a tumor close to the anal sphincter while preserving continence and achieving clear resection margins. ISR, first described by Schiessel, is an alternative to abdominoperineal resection for very low rectal cancer and is considered one of the most technically demanding sphincter-preserving procedures, because it requires precise dissection along the intersphincteric plane deep in the pelvis. TaTME, first reported by Sylla and colleagues in 2010, provides a direct transanal view of the distal mesorectum and may improve visualization of the mesorectal plane, particularly in patients with a narrow pelvis, a bulky mesorectum, or tumors close to the anal verge. The rationale for pairing the two techniques is that the enhanced distal access offered by the transanal route may be especially beneficial when the dissection plane is at its most confined.

Enthusiasm for that rationale has been tempered by safety concerns. Reports from Norway during the early implementation period of TaTME described unexpectedly high local recurrence rates with a multifocal recurrence pattern, prompting international scrutiny of the technique. Subsequent analyses from international registries and large multicenter cohort studies have since demonstrated local recurrence rates comparable to those seen after conventional total mesorectal excision, suggesting that TaTME can achieve acceptable oncological outcomes in a multicenter setting. The new Japanese analysis adds evidence specifically for the very low tumor subgroup, in which achieving adequate margins while preserving the anal sphincter is particularly difficult and in which ISR itself has historically been associated with a relatively higher local recurrence risk due to the extremely distal tumor location and a limited distal margin.

The cohort comprised patients with histologically confirmed primary adenocarcinoma or adenosquamous carcinoma, tumors within 5 centimeters of the anal verge, and clinical stage I to III disease. Among the 224 patients, 161 (71.9 percent) were male and 87 (38.8 percent) received neoadjuvant therapy. The median tumor height from the anal verge was 4.0 centimeters, with an interquartile range of 3.0 to 5.0, and approximately 44.6 percent of tumors were located in the anterior or circumferential wall. Fourteen patients (6.3 percent) had clinical T4 disease, 64 (28.6 percent) had clinical lymph node metastasis, and 76 (33.9 percent) received adjuvant therapy. No minimum requirement for institutional TaTME volume or surgeon experience was specified for participation; the median surgeon had performed 12 TaTME procedures and the median annual institutional volume was 12.5 cases.

Operative details highlight the scale and complexity of the procedure. The median total operation time was 386 minutes, and the median estimated blood loss was 50 milliliters. Lateral pelvic lymph node dissection was performed unilaterally in 19 patients (8.5 percent) and bilaterally in 46 (20.5 percent). For the abdominal component, 174 patients (77.7 percent) underwent laparoscopic surgery and 48 (21.4 percent) robotic surgery. Intraoperative adverse events during transanal dissection included purse-string suture failure in six patients (2.7 percent), rectal perforation in two (0.9 percent), and vaginal injury in two (0.9 percent); no urethral or autonomic nerve injuries occurred, and conversion to open surgery was not observed in any case. Clavien-Dindo grade 2 and grade 3 postoperative complications occurred in 52 (23.2 percent) and 21 (9.4 percent) patients respectively, no mortality was recorded, and reoperation was required in six patients (2.7 percent).

Pathological findings underscored how advanced some of these tumors were despite the sphincter-preserving intent. The median tumor diameter was 26 millimeters, four patients (1.8 percent) had pathological T4 disease, and 45 (20.1 percent) had pathological lymph node metastasis. Lateral pelvic lymph node metastasis was observed in seven patients (3.1 percent), perineural invasion in 30 (13.4 percent), and a positive circumferential or radial margin in eight (3.6 percent); the distal margin was positive in two patients (0.9 percent). Among the 87 patients who received neoadjuvant therapy, a good pathological response was seen in 32 (36.8 percent). Because the original database recorded the circumferential resection margin and radial margin as a single variable, the investigators analyzed them jointly as CRM/RM positivity, defined as a distance of 1 millimeter or less between the deepest tumor invasion or metastatic lymph node and the relevant soft tissue margin.

After a median follow-up of 4.3 years, local recurrence was identified in 16 patients within 3 years. The recurrence locations were the central pelvis in five patients (2.3 percent), the lateral pelvis in nine (4.2 percent), and anastomotic sites in two (0.9 percent); a multifocal pattern was observed in two of the 16 patients (12.5 percent). The median time to local recurrence was 1.9 years. The 3-year recurrence-free survival rate was 79.5 percent (95 percent confidence interval 73.5 to 84.3) and the 3-year overall survival rate was 98.1 percent (95 percent confidence interval 95.1 to 99.3). Salvage surgery was feasible in a subset of patients with isolated local recurrence: of the 15 patients who had local recurrence only, eight underwent salvage surgery and all were alive and disease-free at the end of follow-up, while five received palliative chemotherapy, one received radiotherapy, and one received no treatment.

The risk factor analysis produced a clear central finding. Univariate analysis identified six factors associated with local recurrence: histopathological classification, lymphatic invasion, vascular invasion, perineural invasion, tumor budding, and CRM/RM status. No significant differences were found for clinical T or N category, stage, the number of TaTME procedures performed by the surgeon, hospital TaTME volume, or the use of preoperative or postoperative treatment, and exploratory cutoffs of 40 procedures for surgeon experience and 14 cases per year for institutional volume showed no significant differences in local recurrence, recurrence-free survival, or overall survival. In the multivariable Cox proportional hazards model, CRM/RM positivity emerged as the only significant factor, with a hazard ratio of 8.59 (95 percent confidence interval 1.21 to 61.15). The 3-year local recurrence rate was 6.6 percent in patients without CRM/RM positivity and 37.5 percent in those with it.

To explore the cumulative weight of tumor biology, the investigators constructed an exploratory biologic aggressiveness score from five pathological factors significantly associated with local recurrence in univariate analysis: histopathological classification, lymphatic invasion, vascular invasion, perineural invasion, and tumor budding. Each factor contributed one point, yielding an unweighted composite score that ranged from 0 to 4 in this cohort, since no patient had all five factors. The 3-year cumulative local recurrence rate rose stepwise with the score: 1.4 percent in patients with no adverse factors, 7.3 percent in those with one factor, and 15.6 percent in those with two to four factors. The authors emphasize that the score was constructed post hoc using factors identified in the same cohort and was not externally validated, so it should be regarded as an exploratory measure rather than a validated predictive model, and further validation in independent cohorts is required before clinical application.

The study has limitations that shape how the results should be read. The retrospective design may have introduced selection bias, and although a standardized TaTME protocol was referenced, the abdominal approach, rectal closure technique, and lavage protocol were not strictly standardized across institutions. Pathological evaluations were not centrally reviewed, margin assessment was not standardized, and the circumferential and radial margins could not be distinguished at the individual patient level. Data on perineural invasion and CRM/RM status were missing for 49 and 14 patients respectively, baseline MRI findings on threatened margins were not consistently available, and preoperative MRI-EMVI status was not collected. Anorectal function and quality of life were not assessed, and longer follow-up is needed to evaluate long-term outcomes including distant metastasis. The authors also note that lateral pelvic recurrence, classified here as local recurrence, may reflect anatomical factors beyond the technical quality of the TaTME procedure itself, and that direct comparison with other series is difficult. Within those constraints, the investigators conclude that TaTME combined with ISR appears to be a feasible sphincter-preserving option for lower rectal cancer, with acceptable local recurrence rates and favorable survival outcomes, and that achieving margin-negative resection and careful postoperative surveillance in patients with adverse pathological features remain essential.

Subject of Research: Oncological outcomes and risk factors for local recurrence after transanal total mesorectal excision with intersphincteric resection for lower rectal cancer

Article Title: Local Recurrence and Oncological Outcomes After Transanal Total Mesorectal Excision With Intersphincteric Resection for Lower Rectal Cancer: A Nationwide Multicenter Cohort Study (Ta‐Ta‐Mi Study)

Article References: Tanabe, K., Mori, S., Baba, K., Matsuda, T., Takemasa, I., Okabayashi, K., Tani, C., Manabe, T., Kakeji, Y., Ohtsuka, T., Yamamoto, S., Naitoh, T., & Ta‐Ta‐Mi Study Group Collaborative of the Japan Society of Laparoscopic Colorectal Surgery (2026). Local Recurrence and Oncological Outcomes After Transanal Total Mesorectal Excision With Intersphincteric Resection for Lower Rectal Cancer: A Nationwide Multicenter Cohort Study (Ta‐Ta‐Mi Study). Annals of Gastroenterological Surgery, Article ags3.70304. https://doi.org/10.1002/ags3.70304

Image Credits: AI Generated

DOI: 10.1002/ags3.70304

Keywords: rectal cancer, transanal total mesorectal excision, intersphincteric resection, local recurrence, sphincter-preserving surgery, circumferential resection margin, radial margin, multicenter cohort study, recurrence-free survival, overall survival, tumor budding, Japan