# Diffusion-weighted magnetic resonance imaging as an early prognostic marker of chemoradiotherapy response in squamous cell carcinoma of the anus: An individual patient data meta-analysis

## TL;DR

This study found that MRI-based ADC parameters during treatment do not reliably predict outcomes in anal cancer patients undergoing chemoradiotherapy.

## Contribution

The study is the first individual patient data meta-analysis to evaluate diffusion-weighted MRI as a prognostic marker in anal cancer.

## Key findings

- ADC mean change of <20% was associated with higher locoregional failure rates (16.7%) compared to >20% (8.0%).
- No other ADC histogram parameters were linked to treatment failure in squamous cell carcinoma of the anus.
- The authors recommend integrating radiological biomarkers into larger trials to improve reliability.

## Abstract

•ADC parameters during treatment were not associated with outcome in anal cancer.•Individual patient meta-analysis was useful to increase patient numbers and events.•Radiological biomarkers must be integrated into large anal cancer trials.

ADC parameters during treatment were not associated with outcome in anal cancer.

Individual patient meta-analysis was useful to increase patient numbers and events.

Radiological biomarkers must be integrated into large anal cancer trials.

Squamous cell carcinoma of the anus (SCCA) can recur after chemoradiotherapy (CRT). Early prediction of treatment response is crucial for individualising treatment. Existing data on radiological biomarkers is limited and contradictory. We performed an individual patient data meta-analysis (IPM) of four prospective trials investigating whether diffusion-weighted (DW) magnetic resonance imaging (MRI) in weeks two to three of CRT predicts treatment failure in SCCA.

Individual patient data from four trials, including paired DW-MRI at baseline and during CRT, were combined into one dataset. The association between ADC volume histogram parameters and treatment failure (locoregional and any failure) was assessed using logistic regression. Pre-defined analysis included categorising patients into a change in the mean ADC of the delineated tumour volume above and below 20%.

The study found that among all included 142 patients, 11.3 % (n = 16) had a locoregional treatment failure. An ADC mean change of <20 % and >20 % resulted in a locoregional failure rate of 16.7 % and 8.0 %, respectively. However, no other ADC-based histogram parameter was associated with locoregional or any treatment failure.

DW-MRI standard parameters, as an isolated biomarker, were not found to be associated with increased odds of treatment failure in SCCA in this IPM. Radiological biomarker investigations involve multiple steps and can result in heterogeneous data. In future, it is crucial to include radiological biomarkers in large prospective trials to minimize heterogeneity and maximize learning.