# Analysis of the clinical value of anterior peritoneal reflection for the management of rectal cancer

## TL;DR

This study shows that the anterior peritoneal reflection (aPR) can help guide treatment and predict outcomes in rectal cancer patients more effectively than traditional tumor height measurements.

## Contribution

The study introduces aPR as a novel anatomical landmark for classifying rectal cancer and demonstrates its clinical utility in treatment decisions and prognosis.

## Key findings

- aPR-defined classification predicted lower disease-free survival in middle-to-low rectal cancer compared to upper rectal cancer.
- aPR-based classification was an independent predictor of disease-free survival, unlike the 10-cm classification.
- nCRT with TRG 0–1 improved outcomes only in the aPR-defined middle-to-low rectal cancer subgroup.

## Abstract

Tumor location affects rectal cancer management, but no consensus exists on criteria. The anterior peritoneal reflection (aPR), an anatomical landmark, shows potential for defining tumor location but requires clinical validation. This study evaluated the utility of aPR in guiding neoadjuvant chemoradiotherapy (nCRT) decisions and predicting lateral lymph node (LLN)/distant metastasis patterns.

This single-center retrospective cohort analyzed data from Peking Union Medical College Hospital (Beijing, China) between January 2016 and August 2022. Magnetic resonance imaging (MRI)-measured aPR parameters were pathologically validated. Patients were stratified by aPR-based definition and tumor height (10 cm). Kaplan–Meier survival curves, log-rank tests, and Cox regression were used for prognostic analysis.

Among 588 patients (439 tumors ≥5 cm from the anal verge), MRI identified aPR with an accuracy of 95.4%. For tumors ≥5 cm, aPR-defined middle-to-low rectal cancer showed lower 3-year disease-free survival (DFS) rate than the upper rectal cancer (P = 0.010), while their 3-year overall survival (OS) rates were comparable. Conversely, 10-cm-defined classification showed no DFS or OS differences (both P > 0.2). Cox regression confirmed aPR-defined classification as an independent DFS predictor (HR = 3.19, P = 0.014), while 10-cm classification was non-predictive. nCRT with tumor regression grade (TRG) 0–1 trended toward improved DFS compared with direct surgery (HR = 0.56, P = 0.072). The independent protective effect of nCRT with TRG 0–1 for DFS was exclusive to the aPR-defined middle-to-low rectal cancer subgroup (HR = 0.45, P = 0.026) and not observed in the 10-cm subgroup. aPR-defined classification was independently associated with LLNs on MRI and postoperative pulmonary metastasis.

aPR may guide nCRT decision-making and predict LLN metastasis and postoperative distant organ metastasis.