# Relationship between fibrosis induced by preoperative chemoradiotherapy and real-time tissue elastography of internal anal sphincter

## TL;DR

This study shows that preoperative chemoradiotherapy may cause fibrosis in the internal anal sphincter, leading to tissue hardening detectable via elastography.

## Contribution

First quantitative investigation of the relationship between chemoradiotherapy-induced fibrosis and sphincter elasticity using real-time tissue elastography.

## Key findings

- Patients who received chemoradiotherapy had significantly higher fibrosis in the internal anal sphincter.
- Elastography showed reduced elasticity in patients who underwent chemoradiotherapy compared to those who did not.
- Elasticity decreased as the percentage of fibrosis increased in the sphincter tissue.

## Abstract

It has been suggested that chemoradiotherapy may cause fibrosis of the internal anal sphincter, resulting in sclerosis. However, no report has quantitatively investigated this relationship by using real-time tissue elastography.

To clarify the relationship between fibrosis and elasticity of the internal anal sphincter in patients undergoing surgery for lower rectal cancer with or without preoperative chemoradiotherapy from a histological perspective.

A single-center, prospective cohort study.

The surgical and pathological departments in a tertiary referral university hospital.

Eighteen patients with rectal cancer who underwent abdominoperineal resection between May 2019 and May 2022 were included in the study.

Real-time tissue elastography was performed before surgery to measure internal anal sphincter hardness as “elasticity” (hardest (0) to softest (255); decreased elasticity indicated sclerotic changes). Internal anal sphincter fibrosis was evaluated using Masson’s trichrome and Elastica van Gieson staining. We evaluated internal anal sphincter elasticity after preoperative chemoradiotherapy and preoperatively in patients who did not undergo preoperative chemoradiotherapy and analyzed the correlation with the percentage of internal anal sphincter fibrosis in the resected specimens.

Of the 18 patients, 10 underwent preoperative chemoradiotherapy. A significantly higher percentage of internal anal sphincter fibrosis was observed in the chemoradiotherapy group. Post-chemoradiotherapy elasticity was significantly lower in patients undergoing chemoradiotherapy compared to pre-chemoradiotherapy elasticity and that in patients not undergoing chemoradiotherapy. The analysis of the correlation between internal anal sphincter elasticity and fibrosis showed that elasticity decreased as the percentage of fibrosis increased.

This study was conducted at a single institution, and the number of cases was small. The radiation dose to the anal canal may have differed depending on the location of the tumor, which may have affected internal anal sphincter elasticity.

Internal anal sphincter elasticity may reflect tissue sclerosis associated with fibrosis caused by chemoradiotherapy.

The online version contains supplementary material available at 10.1007/s00384-025-05026-1.