EP517 - Total Mesorectal Excision vs Local Excision and Adjuvant Chemoradiation for Low-risk T2N0 Rectal Adenocarcinoma

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Purpose/Background: The National Comprehensive Cancer Network (NCCN) advises transabdominal total mesorectal excision (TME) for T2N0 rectal adenocarcinoma due to the increased risk of locoregional recurrence associated with LE alone. This recommendation includes patients who undergo LE for cT1 rectal adenocarcinoma with low-risk features and are upstaged post-operatively to pT2 disease. While TME provides excellent oncologic outcomes, it is associated with significant morbidity and impaired post-operative quality of life relative to LE. Adjuvant chemoradiation therapy (aCRT) is a potential strategy to avoid TME in this setting, however data regarding long-term survival and the significance of pathologic features are lacking. We hypothesize that patients with low-risk pT2N0 rectal adenocarcinoma treated with LE and aCRT will have overall survival comparable to those treated with TME.

Methods/Interventions: The National Cancer Database (NCDB) 2004-2019 was queried for patients with clinical stage T1N0 or T2N0 rectal adenocarcinoma who underwent either TME or LE and were found to have pathologic stage T2N0 cancer. Patients were categorized as either having undergone either TME, LE alone, or LE with aCRT (LE+aCRT). Patients were identified as having low-risk rectal adenocarcinoma if their tumor lacked all high-risk pathologic features (poor differentiation, lymphovascular invasion, signet ring or mucinous morphology). The primary outcome of this study was overall survival (OS) and was compared between the groups using Kaplan-Meier survival analysis and Cox Proportional Hazard modeling adjusting for multiple covariates.

Results/Outcomes: A total of 8484 patients were included in this analysis. Of this, 6815 underwent TME, 685 LE+aCRT, and 984 LE alone. Unadjusted survival analysis demonstrated similar OS between the TME and LE+aCRT groups (median months, 159 vs 150, p=0.07), while OS in the LE alone group was decreased (87, p< 0.05) (Figure 1). In multivariable analysis, TME was independently associated with improved OS relative to the LE+aCRT group (HR 1.21, 95% CI 1.01-1.46). Among patients with low-risk rectal cancer, OS was comparable between TME and LE+aCRT (HR 1.25, 95% CI 0.91-1.72).

Conclusion/Discussion: Among patients with low-risk pT2N0 rectal adenocarcinoma, treatment with local excision and adjuvant chemoradiation resulted in overall survival comparable to the standard treatment of transabdominal total mesorectal excision. However, without selecting for low-risk tumors, patients who underwent local excision and adjuvant chemoradiation had decreased overall survival relative to those who underwent total mesorectal excision. This information can assist surgeons in appropriately determining which patients with pT2N0 rectal adenocarcinoma can avoid total mesorectal excision.