Diagnostic accuracy of endoscopy in determining rectal tumor proximity to the peritoneal reflection

Abstract

Treatment of invasive rectal adenocarcinoma is strati ed into upfront surgery versus neoadjuvant chemoradiotherapy, in part, based on tumor distance from the anal verge (AV). This study examines the correlation between tumor distance measurements (endoscopic and MRI) and relationship to the anterior peritoneal re ection (APR) on MRI. MethodsA single-center retrospective study was performed at a tertiary center accredited by the National Accreditation Program for Rectal Cancer (NAPRC). 162 patients with invasive rectal cancer were seen between October of 2018 and April of 2022. Sensitivity and speci city were determined for MRI and endoscopic measurements in their ability to predict tumor location relative to the APR. Results119 patients had tumors endoscopically and radiographically measured from the AV. Pelvic MRI characterized tumors as above (intraperitoneal) or at/straddles/below the APR (extraperitoneal). True positives were de ned as extraperitoneal tumors < 10cm. True negatives were de ned as intraperitoneal tumors > 10cm. Endoscopy was 81.9% sensitive and 64.3% speci c in predicting tumor location with respect to the APR. MRI was 86.7% sensitive and 92.9% speci c. Utilizing a 12cm cutoff, sensitivity of both modalities increased (94.3%, 91.4%) but speci city decreased (50%, 64.3%). ConclusionFor locally invasive rectal cancers, tumor position relative to the APR is an important factor in determining the role of neoadjuvant therapy. These results suggest endoscopic tumor measurements do not accurately predict tumor location relative to the APR, and may lead to incorrect treatment strati cation.When the APR is not identi ed, MRI-reported tumor distance may be a better predictor of this relationship.