Uveal melanoma metastatic to the liver: the role of quantitative and functional MR imaging in the assessment of early tumor response after TACE.

Purpose: To determine if volumetric changes of contrast-enhanced and diffusion-weighted magnetic resonance (MR) imaging can help assess early tumor response and predict survival in patient with metastatic uveal melanoma after a single session of transarterial chemoembolization (TACE). Materials and Methods: This IRB approved retrospective analysis of prospectively enrolled patients included nine patients with a total of 36 lesions who did not undergo previous systemic and/or locoregional therapies. All patients underwent MR imaging 3-4 weeks before and after the first TACE. MR analysis evaluated the lesion characteristics (signal intensities, WHO, RECIST, tumor volume (vRECIST), mRECIST, EASL and volumetric tumor enhancement using the quantitative EASL (qEASL)) in all patients and apparent diffusion coefficient (ADC) values in a subset of patients (n=5). The lesions were segmented using a semi-automatic 3D volumetric software to provide volumetric contrast-enhanced MR imaging in the hepatic arterial phase and ADC. Tumor response was defined as a decrease in volumetric enhancement of ≥ 50 %. Images before and after TACE were compared using the paired t-test with its exact permutation distribution. Survival for responders and non-responders was estimated with the Kaplan-Meier method and compared using the log-rank test with its exact permutation distribution. Results: In targeted lesions, the mean percentage of volumetric tumor enhancement (qEASL) decreased from 63.9% to 36.5% (P = .021). No significant change was observed in target lesions using the other response criteria. In non-targeted lesions, mean WHO, RECIST, vRECIST, mRECIST, EASL and qEASL were significantly increased. Mean volumetric ADC increased from 1.01 ± .26 to 1.22 ± .28 10-3 mm²/s (P = .033), whereas ADC values for non-targeted lesions remained unchanged. Median survival of all patients was 7.1 months. qEASL was the only method to accurately predict survival amongst non-responders and responders (4.8 vs 29.5 months, respectively; P = .024). Conclusion: Volumetric tumor enhancement may be used as a new surrogate biomarker for survival in patient with uveal melanoma metastatic to the liver after a single session of TACE. [Copyright &y& Elsevier]