Objective To investigate the specimen quality of intersphincteric resection with transabdominal transanal mixed approach for rectal cancer in the Chinese Transanal Total Mesorectal Excision Registry Collaborative (CTRC) database.

Methods The retrospective case‑control study was conducted. Based on the concept of real‑world research, the clinicopathological data of 281 pati-ents with rectal cancer in the CTRC database who underwent intersphincteric resection with trans-abdominal transanal mixed approach in 19 medical centers, including the Beijing Friendship Hospital of Capital Medical University et al, from November 15,2017 to December 31,2023 were collected. There were 196 males and 85 females, aged 61(range, 27-87)years. Observation indicators: (1) preoperative examinations; (2) neoadjuvant therapy; (3) postoperative examinations; (4) analysis of influencing factors for positive circumferential margin in surgical specimen of intersphincteric resec-tion for rectal cancer. Measurement data with normal distribution were represented as Mean±SD. Measurement data with skewed distribution were represented as M(range). Count data were described as absolute numbers or percentages. The chi‑square test was used for univariate analysis. Logistic regression model was used for multivariate analysis.

Results (1) Preoperative examinations. Of the 281 patients, 234 cases underwent preoperative pelvic magnetic resonance imaging (MRI) examina-tion. There were 2 cases in clinical stage T0, 3 cases in clinical stage T1, 58 cases in clinical stage T2, 137 cases in clinical stage T3, 24 cases in clinical stage T4, 3 cases in clinical stage Tx, 7 cases missing clinical T staging data. There were 87 cases in clinical stage N0, 68 cases in clinical stage N1, 60 cases in clinical stage N2, 9 cases in clinical stage Nx, 10 cases missing clinical N staging data. There were 30 cases with mesorectal fascia invasion, 53 cases with extramural venous invasion. The distance from lower margin of tumor to anal margin was 41.9(range, 1.0-80.0)mm. (2) Neoadjuvant therapy. Of the 281 patients, 125 cases underwent neoadjuvant therapy, including 39 cases receiving chemo-therapy alone, 6 cases receiving short‑course simultaneous chemoradiotherapy, 5 cases receiving short‑course simultaneous chemoradiotherapy and delayed surgery, 48 cases receiving long‑course simultaneous chemoradiotherapy, 2 cases receiving other treatments, and 25 cases missing neoadju-vant therapy data. (3) Postoperative examinations. Of the 281 patients, 249 cases achieved R₀ resection, 9 cases achieved R₁ resection, and there were 23 cases missing surgical margin data. The maximum tumor diameter, the number of lymph nodes harvested and positive rate of vessel carcinoma embolus were 30.0(range, 0.5-200.0)mm, 13(range, 0-70) and 27.55%(73/265) in 281 patients. There were 252 patients with circumferential margin records, showing positive in 15 cases, with a positive rate as 5.95%(15/252). The minimum distance from deep part of tumor to circumferential margin was 7.0(range, 0-150.0)mm in 252 patients. There were 85 cases with distal margin records, showing positive in 1 case, and the distance from lower margin of tumor to distal margin was 10.0(range, 0-202.0)mm. There were 273 patients with specimen integrity records, which showed intact specimen in 208 cases, fair specimen in 58 cases, poor specimen in 4 cases, unevaluated specimen in 3 cases. There were 7 cases with rectal perforation. Of the 281 patients, cases in pathological stage T0, Tis, T1, T2, T3, T4 were 14, 5, 22, 107, 113, 12, respectively, and there were 8 cases missing pathological T staging data. Of the 281 patients, cases in pathological stage N0, N1a, N1b, N1c, N2a, N2b were 176, 27, 27, 11,20, 12, respectively, and there were 8 cases missing pathological N staging data. Of the 281 patients, there were 4 cases with distant metastasis, 262 cases without distant metastasis, 5 cases not evaluated, and 10 cases missing tumor metastasis data. Of the 125 patients undergoing neoadjuvant therapy, there were 85 cases with tumor regression grade records, including 16 cases as grade 1, 27 cases as grade 2, 19 cases as grade 3, 15 cases as grade 4, 8 cases as grade 5. (4) Analysis of influencing factors for positive circumferential margin in surgical specimen of intersphincteric resection for rectal cancer. Results of univariate analysis showed that preoperative T staging on preoperative pelvic MRI, mesorectal fascia invasion, extramural venous invasion, pathological T staging, and pathological N staging were related factors for positive circumferential margin in surgical specimen of intersphincteric resection for rectal cancer (P<0.05).

Conclusions Intersph-incteric resection with transabdominal transanal mixed approach has good specimen quality and low positive rate of surgical margin. T staging on preoperative pelvic MRI may be related to positive circumferential margin after intersphincteric resection for rectal cancer.