Diffusion-weighted magnetic resonance imaging for predicting and detecting the response of ocular melanoma to proton beam therapy: initial results

PURPOSE:The aim of this study was to investigate the utility of diffusion-weighted magnetic resonance (MR) imaging for prediction and early detection of response to proton beam therapy in ocular melanoma.MATERIALS AND METHODS:Ten ocular melanoma patients treated with proton beam therapy were enrolled in the study. All patients underwent conventional MR imaging and diffusion-weighted imaging (DWI) before the start of therapy, and after 1, 3 and 6 months of therapy. Tumour volumes and apparent diffusion coefficient (ADC) values of ocular lesions were measured at each examination. Tumour volumes and mean ADC measurements of the four examination series were compared; correlation of ADC values and tumour regression was investigated.RESULTS:Mean ADC value of ocular melanomas significantly increased as early as 3 months after therapy; tumour volume significantly decreased as early as 6 months after therapy. The ADC values of ocular melanomas before therapy significantly correlated with tumour regression.CONCLUSIONS:DWI may provide an early surrogate biomarker for prediction and early detection of tumour response to eye-preserving therapies in ocular melanoma.