567P - Interim endoscopic restaging after induction chemotherapy to predict complete response and survival after total neoadjuvant therapy in low rectal cancer: Ad-hoc analysis of the IMPACT trial

Background

Chemoradiotherapy after induction chemotherapy increases the chance of nonoperative management in rectal cancer, but it adds radiation-associated toxicities and postoperative dysfunction. Early prediction of oncologic outcomes before chemoradiotherapy may optimize the treatment. This study aims to investigate whether interim endoscopic restaging after induction chemotherapy predicts complete response and survival outcomes after total neoadjuvant therapy in rectal cancer.

Methods

This study was an ad-hoc analysis of a phase II study (IMPACT trial) which investigated induction FOLFOX plus bevacizumab followed by chemoradiotherapy in patients with locally advanced low rectal cancer. Restaging endoscopy after induction chemotherapy was assessed for major intraluminal response (volume reduction >80 %), ulceration, nodularity, stenosis, and flexible wall extension on insufflation. Association of the findings with complete response (defined as pathologic complete response or clinical complete response over 3 years without local regrowth), 5-year disease-free survival (DFS), and overall survival (OS) were investigated using univariate and multivariate analyses.

Results

Seventy-two patients were eligible for the study including 27 complete responders. Overall 5-year DFS and OS were 82.5 % and 93.8 %. The presence of major intraluminal response (sensitivity 81.5%, specificity 60.0%,), flexible wall extension (48.1%, 75.6%), nodularity (33.3%, 90.9%), and stenosis (22.2%, 95.6%) were associated with complete response. Multivariate analysis revealed flexible wall extension and major intraluminal response as independent predictors of complete response. Major intraluminal response was associated with improved 5-year DFS (94.6% vs 68.8%) and OS (100% vs 87.2%).

Conclusions

Major intraluminal response and flexible wall extension on interim restaging endoscopy after induction chemotherapy provide estimates of complete response and survival after total neoadjuvant therapy. Interim restaging endoscopy is a convenient examination that could support informed decisions to proceed with chemoradiotherapy.

Clinical trial identification

UMIN000011457.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.