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

BACKGROUND: Among patients with rectal cancer treated with total neoadjuvant therapy, it is unclear whether early, postinduction restaging is associated with final tumor response. If so, interim restaging may alter rectal cancer decision-making. OBJECTIVE: To determine whether postinduction restaging with endoscopy and MRI 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: Patients with biopsy-proven rectal cancer who underwent total neoadjuvant therapy with interim (postinduction) restaging. MAIN OUTCOME MEASURES: Association between response assessment on postinduction restaging and final treatment response. RESULTS: One hundred seven patients were analyzed. Patients with postinduction magnetic resonance tumor response grade 1 and 2 or complete endoscopic response were significantly more likely (OR 5.4, p < 0.01 and OR 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 postinduction composite partial (OR 4.1, p < 0.01) or minimal (OR 12.0, p < 0.01) responses. LIMITATIONS: Retrospective analysis and lack of detailed subclassification of partial endoscopic response may have limited the conclusions of these data. The limited sample size may also have biased these conclusions. CONCLUSIONS: Tumor response to induction therapy is associated with the ultimate treatment response to total neoadjuvant therapy among complete or minimal responders; the significance of a partial interim response remains unclear. See Video Abstract.