Is Early, Post-Induction Restaging of Rectal Cancer Undergoing Total Neoadjuvant Therapy Associated With Ultimate Treatment Response?

Background: Among rectal cancer patients treated with Total Neoadjuvant Therapy, it is unclear whether early, post-induction restaging is associated with final tumor response. If so, interim restaging may alter rectal cancer decision-making.

Objective: To determine if post-induction restaging with endoscopy and magnetic resonance imaging is associated with final tumor response.

Design: Retrospective cohort study.

Settings: US tertiary care institution accredited by the National Accreditation Program for Rectal Cancer.

Patients: Biopsy-proven rectal cancer patients who underwent Total Neoadjuvant Therapy with interim (post-induction) restaging.

Main outcome measures: Association between response assessment on post-induction restaging and final treatment response.

Results: 107 patients were analyzed. Patients with post-induction magnetic resonance tumor response grade 1 - 2 or complete endoscopic response were significantly more likely (odds ratio 5.4 [p < 0.01] and odds ratio 3.7 [p = 0.03], respectively) to ultimately achieve a final complete response. Likewise, the odds of a final incomplete response were significantly higher for patients with post-induction composite partial (odds ratio 4.1, p < 0.01) or minimal (odds ratio 12.0, p < 0.01) responses.

Limitations: Retrospective analysis and lack of detailed subclassification of partial endoscopic response may have limited the conclusions of this data. Limited sample size may also have biased these conclusions.

Conclusion: Tumor response to induction therapy is associated with ultimate treatment response to Total Neoadjuvant Therapy among complete or minimal responders; the significance of a partial interim response remains unclear. See Video Abstract.