The apparent diffusion coefficient (ADC) on 3-T MRI differentiates myometrial invasion depth and histological grade in patients with endometrial cancer

Background Diffusion-weighted magnetic resonance imaging (DW-MRI) with apparent diffusion coefficient (ADC) measurement provides additional information about tumor microstructure with potential relevance for staging and predicting aggressive disease in patients with endometrial cancer (EC). Purpose To determine whether ADC values in EC diverge according to the tumor's histologic grade and myometrial invasion depth. Material and Methods A sample of 48 pathologically confirmed cases of EC were reviewed retrospectively. The sample was distributed as follows: G1 (n = 9); G2 (n = 18); G3 (n = 21); with myometrial invasion <50% (n = 31); and with myometrial invasion >= 50% (n = 17). DW images were performed at 3.0T with b factors of 0-1000/mm(2). The region of interest (ROI) was defined within the tumor with T1-weighted and T2-weighted imaging and copied manually to an ADC map. The tumor's grade and myometrial invasion's depth were determined by postoperative histopathological tests. Results The means of ADC(min) and ADC(mean) values were significantly lower for patients with G2 and G3 endometrial tumors than G1. The same tendency was observed in myometrial invasion, as both ADC(min) and ADC(mean) values were lower for patients with deep than for those with superficial myometrial invasion. The cut-off values of the ADC(min) and ADC(mean) that predicted high-grade tumors were 0.69 x 10(-3) mm(2)/s and 0.82 x 10(-3) mm(2)/s, respectively, while those for myometrial infiltration were 0.70 x 10(-3) mm(2)/s (ADC(min)) and 0.88 x 10(-3) mm(2)/s (ADC(mean)). Conclusion ADC(min) and ADC(mean) values correlated with histologic tumor grade and myometrial invasion depth; therefore, it is suggested that ADC on MRI may be a useful indicator to predict malignancy of ECs.