Effectiveness of IVIM/DWI MRI parameters in evaluating anti-PD-1 antibody treatment response in xenograft models in vivo

Motivation: Although intravoxel incoherent motion (IVIM) parameters are garnering attention as a DWI analytical method, their effectiveness in evaluating the immunotherapy efficacy is still largely unvalued. Goal(s): Our goal was to assess if IVIM/DWI parameters reflect tissue changes subsequent to anti-PD-1 antibody treatment in vivo. Approach: Colon (CT26) and breast (4T1) cancer xenograft murine models received the treatment and afterward MR study. Results: fIVIM (flowing blood volume fraction) was significantly lower in the treated tissue in the CT26 model, while no change was observed in the 4T1 model. Also, there was no difference in the lesion size in both models. Impact: The difference of fIVIM (flowing blood volume fraction) parameter and lesion size between two anti-PD-1 antibody-treated xenograft models might reflect a different level of treatment efficacy, which may indicate the IVIM potential to observe tissue heterogeneity.