Utility of diffusion-weighted imaging in association with pathologic upgrading in biopsy-proven grade I endometrial cancer

Background: Prediction of pathologic upgrading is clinically meaningful to identify the optimal candidate of fertility-preserving hormonal treatment in the young patients with biopsy-proven grade I endometrial cancer. Purpose: To investigate the utility of diffusion-weighted imaging (DWI) in association with pathologic upgrading in endometrial cancer. Study Type: Retrospective. Subjects: Preoperative MRI datasets of 221 patients with grade I endometrial cancer on endometrial biopsy (n = 146), dilatation and curettage (n = 66), or either (n = 9). Field Strength/Sequence: 3.0T, including T₂-weighted imaging, DWI with a b-value of 1000 s/mm², and dynamic contrast enhanced imaging. Assessment: The tumor size was determined as the longest diameter of the lesion. The minimum apparent diffusion coefficient (ADC_min) was calculated using histogram analysis of the entire tumor. Statistical Tests: Mann–Whitney U-test, Pearson's chi-square test, Fisher's exact test, intraclass correlation coefficient (ICC) analysis, receiver operating characteristic (ROC) curve analysis, univariate and multivariate logistic regression analysis. Results: Pathologic upgrading was identified in 42 patients (19.0%). Patients with pathologic upgrading had larger tumors and showed lower ADC_min values than those without pathologic upgrading (both P < 0.001). The area under the ROC curve of ADC_min and tumor size was 0.812 and 0.758, respectively. On multivariate analysis, tumor ADC_min ≤0.600 × 10^-3 mm²/s (odds ratio [OR], 11.8; P < 0.001) and tumor size on MRI >3 cm (OR, 3.24; P = 0.009) were independently associated with pathologic upgrading. Upgrading occurred in 23 of 31 patients (74.2%) with ADC_min ≤0.600 × 10^-3 mm²/s and tumor size >3 cm, and in 7 of 114 patients (6.1%) with ADC_min >0.600 × 10^-3 mm²/s and tumor size ≤3 cm. Data Conclusion: Tumor ADC and tumor size on MRI may be useful parameters in association with pathologic upgrading in biopsy-proven grade I endometrial cancer. Level of Evidence: 4. Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;51:117–123.