Comparison of diffusion-weighted MR imaging and FDG PET/CT to predict pathological complete response to neoadjuvant chemotherapy in patients with breast cancer

To compare the use of diffusion-weighted MR imaging (DWI) and 18F-FDG PET/CT to predict pathological complete response (pCR) in breast cancer patients receiving neoadjuvant chemotherapy. Thirty-four women with 34 invasive breast cancers underwent DWI and PET/CT before and after chemotherapy and before surgery. The percentage changes in the apparent diffusion coefficient (ADC) and the standardised uptake value (SUV) were calculated, and the diagnostic performances for predicting pCR were evaluated using receiver operating characteristic (ROC) curve analysis. After surgery, 7/34 patients (20.6%) were found to have pCR. Az values for DWI, PET/CT and the combined use of DWI and PET/CT were 0.910, 0.873 and 0.944, respectively. The best cut-offs for differentiating pCR from non-pCR were a 54.9% increase in the ADC and a 63.9% decrease in the SUV. DWI showed 100% (7/7) sensitivity and 70.4% (19/27) specificity and PET/CT showed 100% sensitivity and 77.8% (21/27) specificity. When DWI and PET/CT were combined, there was a trend towards improved specificity compared with DWI. DWI and FDG PET/CT show similar diagnostic accuracy for predicting pCR to neoadjuvant chemotherapy in breast cancer patients. The combined use of DWI and FDG PET/CT has the potential to improve specificity in predicting pCR. (orig.)