Quantitative volumetric functional MR imaging: an imaging biomarker of early treatment response in hypo-vascular liver metastasis patients after yttrium-90 transarterial radioembolization

Purpose: To evaluate the value of quantitative volumetric functional MR imaging in early assessment of response to yttrium-90-labeled (Y-90) transarterial radioembolization (TARE) in patients with hypo-vascular liver metastases. Materials and methods: Seventy four metastatic lesions in 14 patients with hypo-vascular liver metastases after TARE were included in this retrospective study. Diffusion and contrast-enhanced MR imaging was performed before and early after treatment. All MR images were analyzed by two experienced radiologists. Response by anatomic metrics (RECIST, mRECIST, EASL) and functional metrics (ADC and arterial and venous enhancement) were reported in targeted and non-targeted lesions. A two-sample paired t test was used to compare the changes after TARE. A p value of <0.05 was considered statistically significant. Results: The anatomic metrics did not show any significant changes in both targeted and non-targeted groups. Targeted lesions demonstrated an increase in mean volumetric ADC (23.4%; p = 0.01), a decrease in arterial and venous enhancement (-22.9% and -6.7%, respectively; p < 0.001 and p = 0.002, respectively) 1 month after treatment. Twenty one responding lesions (42%) by RECIST at 6 months demonstrated a significant increase in volumetric ADC (37.2%; p = 0.01), decrease in arterial and venous enhancement (-58.5% and -23.9%, respectively; p < 0.001) at 1 month post-treatment. Responding lesions did not change significantly by anatomic metrics. Conclusions: RECIST, mRECIST, and EASL criteria failed to stratify lesions into responders and non-responders early after TARE in hypo-vascular liver metastasis. Quantitative volumetric functional MR imaging could be a promising tool as a biomarker for predicting early response and can potentially be utilized in clinical trials.