Cytological Analysis of the Surgical Field During Transanal Total Mesorectal Excision for Rectal Cancer: A Prospective Study.

BACKGROUND:An unexpectedly large number of patients experienced local recurrence with transanal total mesorectal excision in Norway. This appears to be associated with cancer cell spillage during surgery. OBJECTIVE:To investigate the surgical field cytology during transanal total mesorectal excision. DESIGN:This was a prospective cohort study. SETTINGS:This study was conducted at a single center between June and December 2020. PATIENTS:Forty patients with rectal cancer underwent transanal total mesorectal excision. Following the irrigation of the surgical field, the water specimens were cytologically evaluated at six representative steps. The first sample was used as an initial control. The second, third, fourth, fifth, and sixth samples were collected after the 1st purse-string suture, rectotomy, the 2nd purse-string suture, specimen resection, and anastomosis, respectively. The clinicopathological features and intraoperative complications of the patients were reviewed. MAIN OUTCOME MEASURES:The primary outcome was to evaluate the presence of cancer cells in washing cytological samples. RESULTS:Of the 40 consecutive patients enrolled in this study, 18 patients underwent neoadjuvant chemoradiotherapy. Incomplete first pursestring suture and rectal perforation were observed in 4 (10.0%) and 3 (7.5%) cases, respectively. In the first sample, 31 (77.5%) patients had malignant cells. Malignant findings were detected in two patients (5.0%) from the second to fifth samples. None of the sixth sample exhibited any malignant findings. LIMITATIONS:This single center study had a small sample size. CONCLUSIONS:Cancer cells were initially detected by cytology, but only a few were observed throughout the procedure; however, cancer cells were not detected in the final surgical field. Further follow-up and novel studies are required to obtain clinically significant findings using cytology during transanal total mesorectal excision. See Video Abstract.