Dynamic contrast-enhanced magnetic resonance imaging evaluation of whole tumour perfusion heterogeneity predicts distant disease-free survival in locally advanced rectal cancer

Aims: To evaluate diffusion-weighted imaging and dynamic contrast-enhanced magnetic resonance imaging for the prediction of disease-free survival (DFS) in patients with locally advanced rectal cancer. Materials and methods: Patients with stage II or III rectal adenocarcinoma undergoing neoadjuvant chemoradiotherapy (CRT) and surgery were eligible. Patients underwent multi-parametric magnetic resonance imaging (diffusion-weighted imaging and dynamic contrast-enhanced) before CRT, during CRT (week 3) and after CRT (1 week prior to surgery). Whole tumour apparent diffusion coefficient (ADC) and Ktrans histogram quantiles (10th, 25th, 50th, 75th, 90th) were extracted for analysis. The associations between ADC and Ktrans at three timepoints with time to relapse were analysed as a continuous variable using a Cox proportional hazard model. Results: Thirty-three patients were included in this analysis. The median follow-up was 4.4 years. No patient had locoregional relapse. Nine patients developed distant metastases. The hazard ratios for after CRT Ktrans 10th (P ¼ 0.035), 25th (P ¼ 0.048), 50th (P ¼ 0.046) and 75th (P ¼ 0.045) quantiles were statistically significant for DFS. The best K trans cut-off point after CRT for predicting relapse was 28 x 10ˉᶟ mL/g/min (10th quantile), with a higher K trans value predicting distant relapse. The 4-year DFS probability was 0.93 for patients with after CRT K trans value >28 x 10ˉᶟ mL/g/min versus 0.45 for patients with after CRT Ktrans value >28 x 10ˉᶟ mL/g/min. ADC was not able to predict DFS. Conclusions: Patients with higher K trans values after CRT (before surgery) in a histogram analysis of whole tumour heterogeneity had a significantly lower 4-year distant DFS and could be considered for more intense systemic therapy.