Additional diagnostic value of MRI in patients with suspicious breast lesions based on ultrasound

Objective:

Biopsy has long been the standard approach in Breast Imaging Reporting and Data System® (BI-RADS) 4 or BI-RADS 5 (American College of Radiology, Reston, VA) lesions despite a wide variation in reported incidence of malignancy in BI-RADS 4 lesions. This study examined the diagnostic value of breast MRI as well as its ability to decrease unnecessary biopsies in patients with solid breast lesions who had an indication for biopsy.

Methods:

In this retrospective study, 277 breast lesions with a documented histological diagnosis as established by ultrasound-guided biopsy were included. All patients were female, and biopsy was performed owing to a BI-RADS score of 4 or 5 on ultrasonography. In addition, all patients had undergone MRI before biopsy. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MRI in predicting malignancy were calculated.

Results:

When all lesions were analysed, sensitivity, specificity, NPV and PPV of MRI in detecting malignancy were 94.2%, 56.1%, 90.7% and 68.1%, respectively. When only ultrasonographic BI-RADS 4 lesions are considered, the corresponding figures were as follows: 90.9%, 56.7%, 93.8% and 46.4%, respectively. False-negative rate of MRI for the latter group of lesions was 2.6%. 42% of unnecessary biopsies were avoided in sonographic BI-RADS 4 lesions.

Conclusion:

Despite promising results obtained in this study, dynamic MRI currently does not seem to be effective in ruling out the need for biopsy in the assessment of sonographic BI-RADS 4 lesions. However, advanced MRI techniques may assist in improving possible benefits of MRI in this patient group.According to data from the American Cancer Society, Atlanta, GA, benign lesions account for nearly 80% of all breast biopsies performed. Although mammography is effective in detecting occult breast cancer, it is also associated with false-positive findings, resulting in the detection of different types of benign tissue in approximately 71–75% of the cases undergoing biopsy owing to suspicious mammography.¹ This usually prompts the clinicians to use ultrasound or MRI to obtain additional information on the character of the lesions. However, this approach has resulted in higher cancer detection yields in females who are at increased risk of breast cancer at the expense of increased false-positivity rates.^2,3Although it may be appropriate to monitor Breast Imaging Reporting and Data System® (BI-RADS) 3 (American College of Radiology, Reston, VA) (probably benign) lesions radiologically owing to their low cancer risk (0.3–1.7%),^4–8 biopsy has long been the standard approach in BI-RADS 4 or BI-RADS 5 lesions. The reported risk of malignancy for BI-RADS 5 lesions is >95%, while a wide variation in reported incidence of malignancy is noted in BI-RADS 4 lesions (from 2% to 95%). Biopsy is recommended for any lesion with an estimated risk of malignancy exceeding 2% based on imaging findings. Therefore, most of the solid lesions visualized through imaging modalities are candidates for biopsy. In recent years, a good deal of research has been devoted to the combined use of different imaging modalities in order to decrease false-positive biopsies and to improve the well-known low specificity of radiological imaging techniques in general and ultrasound in particular. In this regard, breast MRI has been shown to provide a high negative predictive value (NPV) that may help safely exclude a diagnosis of malignancy.^9–12In this study, the diagnostic value of breast MRI as well as its ability to decrease unnecessary biopsies has been examined in a group of patients with solid breast lesions who had an indication for biopsy based on ultrasound results.