Prediction of the therapeutic effect of dienogest in ovarian endometrial cysts using the apparent diffusion coefficient

The purpose of this study was to investigate whether apparent diffusion coefficient (ADC) mean values can be used for predicting the treatment response in ovarian endometrial cyst patients with dienogest (DNG) administration. Eighteen patients received DNG (2 mg/day, orally) for 60 days, among whom 26 ovarian endometrial cysts were retrospectively identified. Mean ADC values of individual ovarian endometrial cysts were obtained by ADC maps inside the tumor. There was a significant correlation between ADC values and reduction ratio. When calculating the mean ADC values for three groups; more than 50%, 50-25% and less than 25%, ADC values significantly increased with increasing reduction ratio; 2.05 × 10(-3)mm(2)/s, 1.28 × 10(-3)mm(2)/s and 0.94 × 10(-3)mm(2)/s, respectively (p = 0.0180). Multiple regression analysis by reduction ratio (%), ADC mean values (× 10(-3)mm(2)/s), tumor longest diameter (cm) and CA125 (U/ml) revealed that tumor reduction ratio by DNG administration could be predicted by the following equation; R = 19.3 + 24.0x - 0.4y + 0.1z (R: Reduction ratio, x: ADC mean, y: Longest diameter, z: CA125). In conclusion, the ADC mean value is useful for the prediction of the treatment response in ovarian endometrial cyst patients with DNG administration.