Risk of recurrence following transanal endoscopic microsurgery without neoadjuvant or adjuvant treatment in T2 rectal cancer.

[BACKGROUND] Transanal endoscopic microsurgery (TEM) is only curative treatment for T1 rectal cancer with low-risk features. In T2 cancer, TEM is not recommended but could be used as a palliative procedure and/or in patients unfit for surgery. Few studies exist investigating recurrence after TEM for T2 rectal cancer.

[METHOD] Retrospective, population-based study using the Swedish Colorectal Cancer Registry. Included patients had T2 rectal adenocarcinoma treated with TEM or surgery without neoadjuvant or adjuvant therapy between 2009 and 2021. Patients lost to follow-up, with syn/metachronous tumours or unknown recurrence status were excluded. Patient characteristics, perioperative morbidity, local and distant recurrence were compared.

[RESULTS] 63 patients treated with TEM and 894 with surgery. Median age was 81 and 70 (p < 0.01). 59 % and 23 % respectively were ASA III-IV (p < 0.01). TEM tumours were more distal, 37 % vs 16 % in the lower third of the rectum (p < 0.01). There were no severe complications after TEM compared to 6 % following surgery (p = 0.04). 5-year local recurrence was 33 % after TEM and 2 % after surgery (HR = 25.58, (p < 0.01). 5-year distant recurrence rate was 9 % after TEM and 7 % after surgery (HR = 0.49, (p = 0.27). Mean time to local recurrence was 16 months after TEM, 34 months after surgery, time to distant recurrence 22 months after both.

[CONCLUSION] TEM for T2 rectal cancer has high risk of local recurrence and cannot be recommended when intent is curative. TEM could be an option for patients unfit for surgery.