This study aims to dynamically assess tumor changes after
variable
treatments with vascular endothelial growth factor (VEGF) inhibitor
and/or immune checkpoint inhibitor (ICI) using multimodal imaging
of MRI and 18F-FDG PET/CT in a hepatocellular carcinoma
(HCC) mice model. Based on different treatments, 24 mice were randomly
divided into four groups: control (isotype-matched IgG antibody 10
mg/kg), VEGF inhibitor (sorafenib 50 mg/kg), ICI (anti-PD-L1 antibody
10 mg/kg), and combination groups (sorafenib 50 mg/kg + anti-PD-L1
antibody 10 mg/kg). Quantitative imaging assessments, including volume
transfer constant (K
trans), apparent diffusion
coefficient (ADC), lactate/choline ratio, and the maximum standardized 18F-FDG uptake value ratio of tumor to muscle (SUVtumor/SUVmuscle ratio), were acquired at different time points
(before treatment and 7, 14, and 21 days after treatment). Quantitative
data were presented as the mean ± standard errors and two-way
repeated-measure ANOVA tests were performed for intergroup and intertime
point comparisons. After 21 days from the initiation of therapies,
combination group showed the lowest tumor volume and weight, followed
by ICI, VEGF inhibitor, and control group, with no significance between
the VEGF inhibitor and control groups. In addition, K
trans values significantly decreased, and the lactate/choline
ratio and SUVtumor/SUVmuscle ratio were significantly
elevated in the VEGF inhibitor group. ADC significantly increased
in the ICI and combination groups, with no significant differences
in ADC observed between the control and VEGF inhibitor groups, which
showed a similar dynamic change to the tumor volume. Furthermore, K
trans, lactate/choline ratio, and ADC were significantly
correlated with CD31+ area, hypoxyprobe+ area,
and apoptosis, respectively. Our results suggest that the singular
treatment and combination of the VEGF inhibitor and ICI treatments
for HCC present different multimodal imaging changes in accordance
with the specific histopathological features. These findings might
facilitate the formulation of better treatment response criteria;
besides, we find ADC is probably an indicator easily to obtain for
treatment response evaluation.