Intravoxel incoherent motion diffusion-weighted imaging for early assessment of combined anti-angiogenic/chemotherapy for colorectal cancer liver metastases

BACKGROUND: To explore the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in the early assessment of colorectal cancer liver metastases (CRLM). METHODS: A total of 34 patients with pathologically confirmed unresectable CRLM were enrolled. All participants uniformly received capecitabine and oxaliplatin (CAPOX) plus bevacizumab chemotherapy as standard first-line treatment for advanced colorectal cancer (CRC). Participants underwent 1.5-T conventional magnetic resonance imaging (MRI) and IVIM-DWI sequence scans with 9 b values (0 to 1,000 s/mm(2)) before treatment and at 3 weeks of treatment, and conventional MRI scans were performed at 6 and 12 weeks after the initial treatment. The IVIM-DWI parameters in the tumor target area were extracted using image post-processing software, including perfusion fraction (f), true diffusion coefficient (D), and false diffusion coefficient (D*). The response assessment was based on the Response Evaluation Criteria in Solid Tumors (RECIST) v. 1.1 by measuring the longest tumor diameter on dynamic contrast-enhanced (DCE) T1-weighted images. RESULTS: According to the RECIST v. 1.1 criteria, the 34 participants were divided into a response group (n=16) and a non-response group (n=18). In the response group, the f value was significantly lowered (P=0.001) and the D value was significantly increased after treatment (P=0.002). In the non-response group, the D value was increased slightly after treatment (P=0.039), and there was no significant difference in the f value and the D* value. In addition, the f value at baseline was significantly greater in the response group than in the non-response group (0.221±0.033 vs. 0.175±0.040; P=0.001). The receiver operating characteristic (ROC) curve analysis showed that the percentage change of the f value obtained the largest area under the curve (AUC =0.797), and the AUC obtained by the Fisher’s linear discriminant analysis (FLDA) method (Δf & ΔD combination) was 0.819. CONCLUSIONS: The IVIM-DWI parameters (f values and D values) provided effective assessment of the therapeutic effect of CAPOX combined with bevacizumab in patients with CRLM at an early stage, and the f value of the pre-treatment tumor area was shown to be useful for predicting the treatment response of patients.