Diffusion-weighted imaging: Apparent diffusion coefficient histogram analysis for detecting pathologic complete...

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Neoadjuvant chemoradiotherapy (CRT) is standard for rectal cancer.
• Evaluating treatment response, specifically pathologic complete response (pCR), is crucial for patient management.
• Preoperative magnetic resonance imaging (MRI) is used to assess tumor stage and response.

Purpose of the Study:

• To assess the utility of apparent diffusion coefficient (ADC) values from histogram analysis of whole rectal tumors.
• To determine if ADC histogram parameters can quantitatively evaluate pCR after neoadjuvant CRT using preoperative MRI.

Main Methods:

• 86 rectal cancer patients undergoing surgery post-neoadjuvant CRT were analyzed.
• Two blinded radiologists performed quantitative image analysis using T2-weighted and diffusion-weighted MRI.
• Dedicated software generated ADC histograms to assess whole tumor ADC distribution.

Main Results:

• 18.6% of patients achieved pCR.
• ADC histogram parameters showed excellent inter-reader agreement.
• Post-CRT ADC histogram values (minimum, 10th, 25th, 50th, 75th percentiles, and mean) were significantly higher in the pCR group.
• The 25th percentile of post-CRT ADC demonstrated the best diagnostic performance for pCR (AUC=0.796).

Conclusions:

• Low percentile ADC values from histogram analysis of rectal cancer on post-CRT MRI significantly differentiate between pCR and non-pCR groups.
• ADC histogram analysis provides a quantitative and objective marker for evaluating complete pathologic response to preoperative CRT in rectal cancer.