Intravoxel Incoherent Motion of Colon Cancer Liver Metastases for the Assessment of Response to Antiangiogenic Treatment: Results from a Pilot Study

Objective: This study was aimed at evaluating the intravoxel incoherent motion (IVIM) parameter alterations of liver metastases of colorectal carcinoma (CRC) during antiangiogenic bevacizumab combination therapy. Methods: Twenty-five patients with CRC liver metastases treated with bevacizumab in combination with FOLFOX-or-FOLFIRI protocols were enrolled in the study. MRI was performed using a 1.5-tesla scanner pre-treatment (PT) and at 3, 6, and 9 months of therapy. Routine abdominal MRI sequences and an IVIM-DWI (diffusion-weighted imaging) sequence were obtained. The IVIM-DWI sequence was executed with 16 b-values varying from 0 to 1,400 s/mm². The mean values of apparent diffusion coefficient (ADC), true diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) of each metastasis were obtained for all b-values, and the time-related changes were recorded to analyze the chronologic responses to antiangiogenic therapy. The RECIST 1.1 criteria were used for the evaluation of treatment response. Results: The diameters of the metastases diminished significantly at 9 months when compared with PT ( p = 0.03). The D ( p = 0.10) and ADC ( p = 0.21) values of the metastases increased at 9 months of therapy. D* was the highest at 3 months ( p = 0.24); it decreased at 6 ( p = 0.97) and 9 months ( p = 0.87) of therapy. The f value had peaked at 3 months ( p = 0.51) and started to decrease thereafter. At 6 months, f decreased to the lowest values ( p = 0.12). Conclusion: IVIM parameters, particularly the perfusion fraction, may quantitatively reflect the response to antiangiogenic treatment. The antiangiogenic response manifests after 3 months of therapy before the RECIST-related response.