Added value of 3D APT histogram analysis to DWI for predicting complete response to neoadjuvant chemoradiotherapy in...

To evaluate the added value of amide proton transfer-weighted (APTw) imaging to diffusion-weighted imaging (DWI) using histogram analysis for assessing pathologic complete response (pCR) in patients with locally advanced rectal cancer (LARC) undergoing neoadjuvant chemoradiotherapy (NCRT).

Sixty-two patients with LARC were enrolled in this prospective study. Magnetic resonance (MR) examinations including APTw, DWI, and T2-weighted imaging (T2WI) were performed before NCRT. Based on histologic assessment, patients were divided into a pCR group or a non-pCR group. APTw and apparent diffusion coefficient (ADC) histogram features were compared between the two groups. Correlations between histogram parameters and tumor regression grading (TRG) categories were assessed using Spearman's correlation analysis. The predictive performances of six models (ADC alone, APTw alone, clincal factors, APTw + ADC, clinical + APTw, APTw + ADC + clinical) were evaluated using the areas under the receiver operating characteristic curve (AUC-ROC).

The pCR group demonstrated significantly lower APTw histogram parameters (including the 85th, 90th, 95th, and 99th percentiles, standard deviation, variance, et al) and higher APTw-1st percentile, skewness, and minimum values vs. non-pCR group(all P < 0.05). Adding APTw imaging to DWI using histogram analysis significantly improved diagnostic performance for predicting pCR (AUC: 0.909) compared to DWI alone(AUC: 0.722, P < 0.05). The combined model (APTw + ADC + clinical) achieved the highest AUC of 0.963. Multiple APTw histogram parameters (e.g., higher percentiles) showed positive correlations with TRG categories (Spearman's ρ range: 0.43-0.65; all P < 0.05).

Adding APTw imaging to DWI using histogram analysis significantly improves diagnostic accuracy for identifying pCR to NCRT in LARC patients compared to DWI alone.