Tumour apparent diffusion coefficient is associated with depth of myometrial invasion and is negatively correlated to tumour volume in endometrial carcinomas

•Low tumour ADC is associated with deep myometrial invasion in endometrial carcinomas.•Tumour ADC value is negatively correlated to tumour size.•Preoperative staging by MRI is prone to considerable interobserver variability.•Interobserver agreement on the measurements of tumour ADC values is good.•Tumour ADC measurement may aid in preoperative identification of high-risk patients.

AimTo explore possible correlations between tumour apparent diffusion coefficient (ADC), morphological tumour volume, and clinical and histological characteristics in endometrial carcinomas and to evaluate interobserver agreement for preoperative staging by MRI and for ADC measurements.Materials and methodsPreoperative conventional MRI including diffusion-weighted imaging (DWI) was performed in 105 endometrial carcinoma patients. Three radiologists independently reviewed the images for the presence of deep myometrial invasion, cervical stromal invasion, and lymph node metastases, and measured tumour ADC in regions of interest (ROIs). ADC values were analysed in relation to histomorphological characteristics and tumour volume. Kappa coefficients (κ) and intraclass correlation coefficients (ICC) for interobserver agreement for MRI staging results and ADC measurements, respectively, were calculated, and receiver operating characteristic (ROC) curves for identification of deep of myometrial invasion were generated.ResultsMean tumour ADC was significantly lower in tumours with deep myometrial invasion (ADC = 0.75 × 10−3 mm2/s) compared to tumours with superficial or no myometrial invasion (ADC = 0.85 × 10−3 mm2/s; p < 0.001). ADC was negatively correlated to tumour size (p = 0.007). The interobserver agreement was fair (κ = 0.32) for depth of myometrial invasion, good for cervical stromal invasion (κ = 0.66), and moderate for lymph node metastases (κ = 0.54), and the interobserver variability for ADC value measurements was low (ICC = 0.60).ConclusionTumour ADC measurements may in the future provide an adjunct tool, aiding in the preoperative identification of high-risk patients with deep myometrial infiltration.