Anorectal functional outcomes after transanal total mesorectal excision (TaTME): a Random Forest analysis to predict patients' outcomes

Background: . Anorectal, sexual and urinary dysfunctions are still common issues after rectal cancer surgery, although seldom explored. Objective: . To investigate the entire spectrum of anorectal urinary, and sexual functional outcomes in patients treated with trans-anal total mesorectal excision (TaTME). Design: Patients with a mid-/low-rectal cancer (1-11 cm from the anorectal junction) treated with TaTME between 2015-2020, were interviewed after surgery using validated questionnaires. Statistical analyses were computed to identify variables correlated with worse outcomes and to provide a decision tree algorithm. Setting: . University Research Hospital, high volume referral center for rectal cancer surgery. Patients . Patients were included if undergoing TaTME with primary anastomosis with or without diverting ileostomy/colostomy. Only patients with a minimum follow-up of 6 months (from stoma reversal or from the primary procedure) were selected. Interventions . Patients were interviewed using the CCFIS - Wexner Scale, LARS score, ICIQ-MLUTS, ICIQ-FLUTS, IIEF and FSFI questionnaires. Main Outcome Measures . The primary outcome measure was the bowel function. Secondary outcomes were urinary and sexual functional data. Results: . Out of 154 patients treated with TaTME, 97 were included (mean age: 66.1 years, M/F 1.7). Sixty-seven percent underwent NAD and 88.7% had a protective stoma. Patients were interviewed in a mean time of 19.0±9.3 months after primary or stoma reversal surgery. Mean Wexner score was 3.8±4.8, whereas mean LARS score was 17.4±13.8. Statistical analyses documented that increased age, operative time and interval to stoma reversal correlated with worse Wexner-LARS categories. The Random Forest analyses documented worse LARS symptoms among patients with an operative time>295 minutes and a stoma reversal performed after more than 5.6 months. Among those who carried a stoma from 3-5.6 months, patients older than 65 years reported anorectal postoperative dysfunction. Limitations. Single center experience with no comparison group. Conclusions: . TaTME can provide good long-term results for the anorectal functions. An algorithm with specific risk categories was provided to identify sub-groups at risk to develop major LARS syndrome.