Objective To analyze the quality of surgical specimens of rectal cancer in the Chinese transanal total mesorectal excision (taTME) registry collaborative (CTRC) database.

Methods The retrospective and descriptive study was conducted. Based on the concept of real‑world research, the clinicopathological data of 1 761 patients with rectal cancer in the CTRC database who underwent taTME in 40 medical centers, including the Beijing Friendship Hospital of Capital Medical University et al, from November 15, 2017 to December 31, 2022 were collected. There were 1 212 males and 549 females, aged 62(range, 53-68)years. Observation indicators: (1) preoperative examinations; (2) neoadjuvant therapy; (3) postoperative examinations. Measurement data with skewed distri-bution were represented as M(range). Count data were described as absolute numbers.

Results (1) Preoperative examinations. Of the 1 761 patients, 1 324 patients underwent preoperative pelvic magnetic resonance imaging examination, and the results showed that 4 cases as clinical T0 stage, 30 cases as clinical T1 stage, 250 cases as clinical T2 stage, 828 cases as clinical T3 stage, 141 cases as clinical T4 stage, 11 cases as clinical Tx stage, 60 cases missing clinical T staging data, 490 cases as clinical N0 stage, 373 cases as clinical N1 stage, 311 cases as clinical N2 stage, 86 cases as clinical Nx stage, 64 cases missing clinical N staging data, 156 cases with mesorectal fascia invasion, 223 cases with extraintestinal blood vessels invasion. The distance from lower margin of tumor to anal margin of 1 324 patients was 50(range, 40-60)mm. (2) Neoadjuvant therapy. Of the 1 761 patients, 873 patients underwent neoadjuvant therapy, including 17 cases receiving radiotherapy alone, 155 cases receiving chemotherapy alone, 43 cases receiving short‑course simultaneous chemoradiotherapy, 26 cases receiving short‑course simultaneous chemoradiotherapy and delayed surgery, 1 case receiving contact radiotherapy, 277 cases receiving long‑course simultaneous chemoradiotherapy, 9 cases receiving other treatments, and 345 cases missing neoadjuvant therapy data. (3) Postoperative examinations. Of the 1 761 patients, 1 584 cases achieved R₀ resection, 23 cases achieved R₁ resection, 1 case achieved R₂ resection, and there were 153 cases missing surgical margin data. The tumor diameter, number of lymph nodes harvest and positive rate of intravascular tumor thrombus were 30(range, 20-45)cm, 13(range, 10-17) and 20.794%(330/1 587) in 1 761 patients. There were 1 647 patients with circumferential margin records, which showed positive in 51 cases, and the minimum distance from deep part of tumor to circumferential margin was 5(rang, 3-13)mm in 1 647 patients. There were 547 cases with distal margin records, which showed positive in 4 cases, and the distance from lower margin of tumor to distal margin was 20(10-25)mm in 547 cases. There were 1 698 patients with specimen integrity records, which showed intact specimen in 1 436 cases, fair specimen in 233 cases, poor specimen in 8 cases, unevaluated specimen in 21 cases, and there were 20 cases with rectal tube perforation. Of the 1 761 patients, cases as pathological T0 stage, Tis stage, T1 stage, T2 stage, T3 stage, T4 stage was 103, 23, 145, 515, 712, 179, respectively, and there were 4 cases of pathology that could not be evaluated and 80 cases missing pathological T staging data. Of the 1 761 patients, cases as pathological N0 stage, N1a stage, N1b stage, N1c stage, N2a stage, N2b stage was 1 117, 189, 133, 66, 109, 68, respectively, and there were 79 cases missing pathological N staging data. Of the 1 761 patients, there were 79 cases with distant metastasis, 1 591 cases without distant metastasis, and 91 cases without data of tumor metastasis. Of the 873 patients undergoing neoadjuvant therapy, there were 405 patients with tumor regression grade records including 105 cases as grade 1, 142 cases as grade 2, 91 cases as grade 3, 43 cases as grade 4, 24 cases as grade 5.

Conclusions In China, the quality of surgical specimens of taTME for rectal cancer is good with low positive rate of resection margin. It is recommended that using a formatted postoperative pathological report for good quality control of pathological report of surgical specimen.