Neuroendocrine liver metastasis treated by using intraarterial therapy: Volumetric functional imaging biomarkers of early tumor response and survival

Purpose: To determine if volumetric changes of diffusion-weighted and contrast material-enhanced magnetic resonance (MR) imaging can help assess early tumor response to intraarterial therapy (IAT) in neuroendocrine liver metastasis (NELM). Materials and This retrospective single-center comprehensive imaging Methods: analysis was performed in compliance with HIPAA and was institutional review board approved. Informed patient consent was waived. Seventy-one patients (39 men; mean age, 62.3 years) with NELM treated with IAT were analyzed retrospectively. MR studies were performed before and 3-4 weeks after therapy. The index lesion was segmented to provide volumetric functional analysis of apparent diffusion coefficient (ADC) and contrast-enhanced MR imaging in the hepatic arterial phase (HAP) and portal venous phase (PVP). Tumor response was defined as increase in volumetric ADC of 15% or greater and decrease in volumetric enhancement of 25% or greater during the HAP or of 50% or greater during the PVP. Patient overall survival was the primary end point after therapy initiation. Univariate analysis included Kaplan-Meier survival curves. The Cox proportional hazards regression model was used to detect interactions between volumetric ADC and contrast-enhanced MR imaging and to calculate the hazard ratio. Results: There was significant increase in mean volumetric ADC (27%, P <.0001) and significant decrease in mean volumetric enhancement during the HAP (225.3%, P <.0001) and the PVP (222.4%, P <.0001) in all patients. Patients who had 15% or greater volumetric ADC increase (n = 49) after therapy had better prognosis than those who had less than 15% increase in volumetric ADC (n = 22) (log-rank test, P <.002). Patients who had 25% or greater decrease in volumetric arterial enhancement (n = 40) or 50% or greater decrease in venous enhancement (n = 18) had better prognosis than those who had less than 25% decrease in volumetric arterial enhancement (n = 31) or less than 50% decrease in venous enhancement (n = 53) (log-rank test, P <.02). Conclusion: Volumetric functional MR imaging criteria may act as biomarkers of early response, indicating that these criteria may be important to incorporate in future NELM clinical trials.