SSAT - EVALUATING TOTAL MESORECTAL EXCISION QUALITY IN THE ERA OF TOTAL NEOADJUVANT THERAPY

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EVALUATING TOTAL MESORECTAL EXCISION QUALITY IN THE ERA OF TOTAL NEOADJUVANT THERAPY
Meghan E. Lark^*¹, Kristen N. Kaiser¹, Samantha Hendren¹, Bruce Robb¹, Scott Dolejs², Sanjay Mohanty¹
¹General Surgery, Indiana University School of Medicine, Indianapolis, IN; ²Franciscan Health Inc, Indianapolis, IN

Introduction:
Total neoadjuvant therapy (TNT) has emerged as an important treatment regimen for locally advanced rectal cancer (LARC). The paradigm shift from standard chemoradiotherapy (CRT) to TNT evolved in an effort to improve treatment compliance and reduce rates of micro-metastases and recurrence. Despite this, recent evidence has suggested that TNT utilization may be associated with increased surgical difficulty and subsequent increased rates of breached total mesorectal excision (TME). This study uses investigates the relationship between neoadjuvant treatment regimens and surgical quality, as well as determine patient and institutional factors associated with poorer surgical quality for LARC.

Methods:
A retrospective analysis was conducted of patients with LARC (cT3-4, N0 or T1-2+, N any) from the National Cancer Database from 2016-2021. After exclusion of patients with metastatic disease and no documented therapy, the cohort was stratified into TNT and CRT groups. Patient demographics, institutional characteristics, and surgical quality measures (rates of circumferential margin (CRM) and proximal/distal margin positivity) were compared between treatment groups. Using a composite measure of surgical quality (all margins negative or ? 1 margin positive) as the outcome, regression methods were used to assess factors associated with poor surgical quality.

Results:
Of 28,957 total patients with LARC, 16,364 (56.6%) received TNT and 12,593 (43.4%) received CRT. Patients receiving TNT were younger than patients receiving CRT (57 years vs 62 years, p<0.001). Factors associated with higher rates of TNT compared to CRT included non-Hispanic White patients (56.6% vs. 43.3%, p<0.001), private insurance (62.9% vs 52%, p<0.001), and academic facility type (58.1% vs. 41.9%, p <0.001). Overall, CRM and proximal/distal margin positivity was observed in 1,538 (5.3%) and 1,714 (5.9%) patients in the cohort. No significant differences in CRM positivity rates were detected between treatment regimens, however patients receiving TNT had higher rates of proximal/distal margin positivity compared to CRT (6.3% vs. 5.3%, p<0.001). On logistic regression, predictors of margin positivity were male sex (OR 1.304, 95% CI 1.185-1.437) and insurance status (OR 1.11, 95% CI 1.058-1.175). Annual facility case volume was stratified into 4 groups (0-5, 6-10, 11-15, 16+) and was associated with a reduction in margin positivity as volume increased (OR 0.935, 95% CI 0.893-0.979). Neoadjuvant treatment regimen was not significantly associated with margin positivity.

Conclusion:
In this national database, TNT was not associated with poorer surgical quality when compared to CRT. As TNT continues to grow as a treatment for selected LARC patients, the degree to which lower local recurrence rates are mediated by surgical quality should be characterized to guide decision-making.

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