Diffusion-weighted magnetic resonance imaging for the prediction of pathologic response to neoadjuvant chemoradiotherapy in esophageal cancer

Purpose: To explore the value of diffusion-weighted magnetic resonance imaging (DW-MRI) for the prediction of pathologic response to neoadjuvant chemoradiotherapy (nCRT) in esophageal cancer. Material and methods: In 20 patients receiving nCRT for esophageal cancer DW-MRI scanning was performed before nCRT, after 8-13 fractions, and before surgery. The median tumor apparent diffusion coefficient (ADC) was determined at these three time points. The predictive potential of initial tumor ADC, and change in ADC (ΔADC) during and after treatment for pathologic complete response (pathCR) and good response were assessed. Good response was defined as pathCR or near-pathCR (tumor regression grade [TRG] 1 or 2). Results: A pathCR after nCRT was found in 4 of 20 patients (20%), and 8 patients (40%) showed a good response to nCRT. The ΔADC_during was significantly higher in pathCR vs. non-pathCR patients (34.6% ± 10.7% [mean ± SD] vs. 14.0% ± 13.1%, p = 0.016), as well as in good vs. poor responders (30.5% ± 8.3% vs. 9.5% ± 12.5%, p = 0.002). The ΔADC_during was predictive of residual cancer at a threshold of 29% (sensitivity of 100%, specificity of 75%, PPV of 94%, and NPV of 100%), and for poor pathologic response at a threshold of 21% (sensitivity of 82%, specificity of 100%, PPV of 100%, and NPV of 80%). Conclusions: In this exploratory study, the treatment-induced change in ADC during the first 2-3 weeks of nCRT for esophageal cancer seemed highly predictive of histopathologic response. Larger series are warranted to verify these results.