Magnetic resonance imaging with dynamic contrast enhancement in the discrimination of mammographically revealed asymmetric density: a prospective cohort study

Le résumé fourni par la source

INTRODUCTION: Breast cancer (BC) is one of the most complex and significant problems in modern clinical oncology. This malignancy demands a multidisciplinary approach to improve survival, in which early detection plays a key role. Currently, mammography remains the only screening modality with relatively high sensitivity, but its specificity is only moderate. It is particularly difficult to differentiate BI-RADS 3 findings, for which the probability of malignancy does not exceed 2%. Asymmetric density represents one such finding, observed in 1–2% of all mammograms. In this context, magnetic resonance imaging (MRI) which does not use ionizing radiation and allows tissue characterization based on both intrinsic MR signal and contrast uptake and wash‑out kinetics — is of particular interest. OBJECTIVE: To evaluate the diagnostic performance of dynamic contrast‑enhanced breast MRI in differentiating mammographically detected asymmetric densities. MATERIALS AND METHODS: We included 57 women (mean age 43.13±6.57 years) who had an asymmetric density on mammography. For all women, we obtained the clinical history and performed a physical breast examination. We also reviewed the findings of other breast imaging modalities. Breast MRI was performed using a Siemens Amira 1.5 T scanner (Siemens, Germany). For contrast enhancement, we administered gadobutrol (7.5 mL, 1 mmol; infusion rate 3–5 mL/s). Lesion verification was achieved by histopathological examination or a minimum 3‑year follow-up. Statistics: normally distributed continuous variables were compared using the Student t-test; non-normally distributed variables were analyzed with the Wilcoxon signed-rank test or the χ 2 test, as appropriate. Statistical significance was set at р< 0.05. Sensitivity, specificity, and positive predictive value were calculated from 2×2 contingency tables. RESULTS: True asymmetric densities without a focal lesion comprised physiological asymmetries caused by uneven distribution of glandular or fibrous tissue, as well as asymmetric breast edema. The former was observed in the majority of cases (50.86%). These cases demonstrated typical asymmetric islands of glandular and fibrous tissue, the summation of which could produce the mammographic finding. Asymmetric breast edema could be caused by inflammatory breast cancer or various benign conditions and was found relatively infrequently (3.51% of all cases). Malignant edema was characterized by signs of regional lymph node metastasis or by parenchymal areas with suspicious enhancement kinetics. True asymmetric densities caused by focal lesions were attributable to breast cancer (12.28%) or benign masses (22.81%). Contrast enhancement in the area of asymmetry was observed in 49.12% of patients. Type I (persistent) enhancement was seen in 50.0% of cases without malignancy, yielding a positive predictive value for benign asymmetry of 100%. Type II (plateau) enhancement was found in 25.0% of cases; its sensitivity and specificity for breast cancer were 60.0% and 82.61%, respectively. Type III (washout) enhancement was observed in 25.0% of patients, with sensitivity and specificity for breast cancer of 40.0% (p<0.001) and 78.26% (р=0.053), respectively. DISCUSSION: Technical asymmetric densities resulting from differences in exposure, compression, or breast positioning during mammography are usually easy to recognize and require technically adequate images for interpretation. Iatrogenic asymmetries (postsurgical scars) were common (14.04% of our series) but are readily identified on clinical examination. CONCLUSION: The sensitivity of dynamic contrast-enhanced MRI for detecting invasive breast cancer in areas of mammographic asymmetry was 100%, but its specificity was only moderate (69.57%).

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.