Value of DCE-MRI and FDG-PET/CT in the prediction of response to preoperative chemotherapy with bevacizumab for colorectal liver metastases

Background: The purpose of this study was to assess the role of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and 18 F-fluorodeoxyglucose positron emission tomography computed tomography (FDG-PET/CT) for evaluation of response to chemotherapy and bevacizumab and for prediction of progression-free survival (PFS) in patients with metastatic colorectal cancer (mCRC) with potentially resectable liver lesions. Methods: A total of 19 mCRC patients were treated with FOLFOX/FOLFIRI and bevacizumab followed by surgery. Dynamic contrast-enhanced magnetic resonance imaging and FDG-PET/CT were performed before treatment and after cycle 5. PET results were quantified by calculating maximum standardised uptake value (SUV max ) whereas area under the enhancement curve (AUC), initial AUC (iAUC) and the endothelial transfer constant (K trans ) were used to quantify DCE-MRI. Pathological analysis of the resection specimen was performed, including measurement of microvessel density (MVD) and proliferation index. Results: Both AUC and iAUC were significantly decreased following bevacizumab therapy (median change of 22% ( P =0.002) and 40% ( P =0.001) for AUC and iAUC, respectively). Progression-free survival benefit was shown for patients with >40% reduction in K trans ( P =0.019). In the group of radiological responders, the median baseline SUV max was 3.77 (IQR: 2.88–5.60) compared with 7.20 (IQR: 4.67–8.73) in nonresponders ( P =0.021). A higher follow-up SUV max was correlated with worse PFS ( P =0.012). Median MVD was 10.9. Progression-free survival was significantly shorter in patients with an MVD greater than 10, compared with patients with lower MVD (10 months compared with 16 months, P =0.016). Conclusion: High relative decrease in K trans , low follow-up SUV max and low MVD are favourable prognostic factors for mCRC patients treated with bevacizumab before surgery.