Three-year oncological outcomes of endoscopic intermuscular dissection for suspected deep submucosal invasive rectal cancer

Aims Endoscopic intermuscular dissection (EID) was recently introduced as a resection technique for deep submucosal invasive rectal cancer (D-SMIC) and has shown encouraging technical and short-term results¹. The aim of this study was to evaluate the 3-year oncological outcomes of EID, with a focus on D-SMIC patients with no or one additional histological risk factor who did not undergo completion total mesorectal excision (cTME) after EID [1].

Methods This prospective cohort study analysed data from consecutive patients treated with EID for suspected rectal D-SMIC at 2 academic hospitals in the Netherlands between 2018-2022. Superficial submucosal invasive cancer (S-SMIC) was defined as Sm1 and D-SMIC as Sm2-3. Tumors were considered high-risk if one of the following histological risk factors were present: high-grade tumor differentiation, lymphovascular invasion, tumor budding grade 2-3, R1/Rx resection margins (< 0.1 mm) or≥pT2 invasion. Patients with low-risk D-SMIC and patients with high-risk lesions who did not undergo cTME after EID were actively monitored with biannual MRI and scar inspection for 2 years, followed by annual examinations for 3 years. Colonoscopy was performed at 1 and 4 years. CEA levels were checked biannually for 5 years. Study outcomes included the 3-year rates of locoregional recurrence (LRR), distant recurrence (DRR), non-salvageable recurrence (nSRR) and rectal preservation, estimated with the Aalen-Johansen method. Locoregional recurrence was defined as intramural or mesorectal nodal cancer recurrence, distant recurrence as any other cancer recurrence, non-salvageable recurrence as cancer recurrence that could not be treated with curative intent, and rectal preservation as the absence of completion or salvage TME following EID.

Results EID was initiated in 188 patients (median age 67 years, 33% female, median lesion size 25 mm) and successfully completed in 177 (94%). Histology showed non-invasive histology in 20 (11%), S-SMIC in 9 (5%), D-SMIC in 94 (53%), and≥pT2 in 53 (30%) patients. R0 resection rates within these groups were 100%, 100%, 92% and 57%, respectively. Of the 94 D-SMIC cases, 35 (37%) had no additional risk factors and 32 (34%) had one risk factor. Active surveillance after EID was initiated in 35/35 (100%) and 23/32 (72%), respectively. Median follow-up was 30 months (IQR 18-48). The estimated 3-year LRR, DRR and nSRR for D-SMIC with no additional risk factor were 7% (95%CI 1-28%), 0% and 0%, respectively. For D-SMIC with one additional risk factor, these rates were 13% (95%CI 2-35%), 0% and 0%, respectively. Of all 188 patients who underwent EID for suspected rectal D-SMIC, the 3-year rectal preservation rate was 65% (95%CI 58-72%).

Conclusions EID followed by active surveillance appears to be a safe alternative to cTME in patients with D-SMIC and no or one additional histological risk factor, preventing rectal surgery in a significant proportion of patients. However, these findings require confirmation in a larger prospective cohort study with longer follow-up.

Publication History

Article published online:
27 March 2025

• References

• 1 Moons LMG, Bastiaansen BAJ, Richir MC, Hazen WL, Tuynman J, Elias SG, Schrauwen RWM, Vleggaar FP, Dekker E, Bos P, Fariña Sarasqueta A, Lacle M, Hompes R, Didden P.. Endoscopic intermuscular dissection for deep submucosal invasive cancer in the rectum: a new endoscopic approach. Endoscopy 2022; 54 (10): 993-998