Introduction

Endoscopic intermuscular dissection (EID) was recently introduced as a novel resection technique for deep submucosal invasive rectal cancer (D-SMIC)¹. While short-term outcomes are promising, intermediate- and long-term oncological safety has not yet been established. Therefore, we aimed to evaluate the 3-year oncological outcomes of EID for suspected rectal D-SMIC.

Aims & Methods

In this prospective cohort study, data of consecutive patients treated with EID for suspected rectal D-SMIC at two academic hospitals in the Netherlands between 2018 and 2022 were analyzed. Superficial submucosal invasive cancer (S-SMIC) was defined as Sm1 and D-SMIC as Sm2-3. Tumors were considered high-risk if they exhibited at least one of the following histological risk factors: high-grade tumor differentiation (G3), lymphovascular invasion, tumor budding grade 2-3, R1/Rx resection margins (<0.1 mm), or ≥pT2 invasion. Patients with D-SMIC or ≥pT2 invasion who did not undergo further treatment after EID, either due to the absence of additional risk factors or based on patient preference, underwent close surveillance. This surveillance involved biannual MRI and endoscopic scar inspection for 2 years, followed by annual MRI and endoscopy for 3 years. A complete colonoscopy was performed after 1 and 4 years. CEA blood levels were measured every six months for 5 years. Study outcomes included the 3-year locoregional recurrence rate (LRR), 3-year distant recurrence rate (DRR), 3-year salvageable recurrence rate (SRR) and 3-year rectal preservation rate. The 3-year estimates were calculated using the Kaplan-Meier method. Locoregional recurrence was defined as intramural cancer recurrence and/or mesorectal lymph node metastasis, while distant recurrences referred to other cancer recurrences. Salvageable recurrence was defined as cancer recurrence that could be treated with curative intent. Rectal preservation was defined as the absence of completion total mesorectal excision (TME) following EID or cancer recurrence.

Results

EID was initiated in 188 patients (median age 67 years, 33% female, 85% ASA I-II, 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%) cases. R0 resection rates within these groups were 100%, 100%, 93% and 58%, respectively. Among the 94 D-SMIC cases, 35 (37%) had no histological risk factors other than deep submucosal invasion. Out of the D-SMIC cases, 72/94 (77%) followed a rectal preserving strategy (64/72 close surveillance and 8/72 adjuvant chemoradiotherapy), while 22/94 (23%) underwent completion TME. The median follow-up period within the D-SMIC group was 30 months (IQR 18-48). At three years, the LRR was 5.9% (95%CI 0.0-11.5%) and the DRR was 1.1% (95%CI 0.0-3.4%). The 3-year SRR was 100% (95%CI 100-100%). One patient (1.1%) died of a non-CRC-related cause. Among the subgroup of 35 D-SMIC cases without additional histological risk factors, all of whom underwent close surveillance following EID, no recurrences occurred within the first three years of follow-up. Beyond this period, one locoregional recurrence (2.9%) occurred at 37 months and one distant recurrence (2.9%) at 51 months, both salvageable. Overall, the 3-year rectal preservation rate among all 188 patients who underwent EID for suspected rectal D-SMIC, was 64.6% (95%CI 58.0-71.9%).

Conclusion

EID for suspected rectal D-SMIC resulted in favorable 3-year rectal preservation rates and demonstrated excellent 3-year oncological outcomes for rectal D-SMIC without additional risk factors.

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 Oct;54(10):993-998.