Diffusion-weighted MR imaging allows monitoring the effect of combretastatin A4 phosphate on rabbit implanted VX2 tumor model: 12-day dynamic results

Abstract

Objectives: To investigate the 12-day dynamic characteristics of tumor response to intravenous administration of CA4P in rabbit VX2 tumor models.

Methods: Study protocol was approved by local ethical committee for animal care and use. Sixteen rabbits with 32 tumors on bilateral legs were randomly divided into treated and control groups. Conventional and DWI images were acquired before and 24 h, 4 days, 8 days and 12 days after treatment. The dynamic changes of tumor on images were correlated with histological results. ADCs were compared among and between groups at different time points.

Results: The tumors in treated group grew slower than those in control group. In treaded group, the mean ADC decreased slightly at 24 h point due to cell edema caused by ischemia. Then, it increased significantly at 4 days and 8 days because of progressive central necrosis. Finally, peripheral tumor proliferation caused a second decrease of ADC at 12 days. The significant difference of ΔADC% between the two groups at 24 h, 4 days and 8 days indicated that the change of ADC in treated group was really caused by CA4P.

Conclusion: The dynamic histological changes of tumor caused by CA4P as reflected exactly by diffusion-weighted MR imaging indicate a noninvasive measure for monitoring tumor vascular targeting treatment.