7T MRI and histology reveal early tissue and perfusion changes after radiofrequency ablation in a murine colorectal cancer model.

Considering neo-angiogenesis as one of the most important hallmarks of solid tumors and a key promoter of recurrence, perfusion studies represent a modality to investigate tumor's vascularization and to identify its influence on chemotherapy efficacy. To analyze neoplastic tissue adjacent to radiofrequency thermal-ablation (RFA) areas to demonstrate early perfusion anomalies and to suggest the synergic role of ablative techniques with chemotherapy treatments. In this prospective study, a total of 10 mice were subjected to a colon-carcinoma cell implantation and after the tumor colonization the RFA procedure was performed. All mice underwent a 7T MRI including 2D single-echo single-shot Dynamic-Contrast-Enhanced (DCE) sequences with intravenous injection of Gadolinium-based contrast agent (CA), before and after 72 h from RFA treatment. Data-driven segmentation of the tumor mass enabled the identification of three ROIs with peculiar pharmacokinetic profiles of CA uptake: VTA, viable tumor area; PNA, partial necrotic area; CNA, complete necrotic area. Within these ROIs, permeability (K-trans and Extravascular-extracellular volume, Ve) and perfusion (Time to Peak, TTP) indices were evaluated with non-parametric paired samples Wilcoxon tests. Robust increase of Ve (PNA and VTA, p = 0.014, p < 0.001, respectively) and TTP (VTA, p < 0.01) is consistent with severe cellular and vascular damage induced by RFA. Perfusion MRI enables robust detection of significant modulation of the microvasculature within 72 h from radiofrequency induced ablation in a murine model of colon-carcinoma. This opens a potentially new time window for the evaluation of therapeutic effects of RFA-enhanced chemotherapy.