Background: The American College of Radiology has established guidelines for outcomes monitoring known as the Breast Imaging Reporting and Data System (BIRADS). These recommendations include calculation of positive predictive values (PPV) and tracking of both benign and malignant histology. We collected this data for 688 radiographically guided biopsies and organized it according to the BIRADS assessment categories. The objective was to evaluate the contribution of the BIRAD System when used to stratify PPV, histology, and biopsy modality data according to the overall assessment rating.
Study design: This study included data from 688 image-guided biopsies. Mammographic studies were either assigned a BIRADS rating at the time of examination or, if the image was taken before our use of BIRADS, examined retrospectively and rated. In these retrospective cases, the histologic outcomes of the biopsy remained unknown to the radiologist until ratings were assigned. Positive predictive value was calculated for each BIRADS category.
Results: The overall PPV for the sample was 0.23. The PPVs increased with increasing level of suspicion as follows: category 1 (0.0), category 2 (0.04), category 3 (0.03), category 4 (0.23), category 5 (0.92). Category 1 lesions represented 0.1% of the biopsies; category 2, 3.6%; category 3, 46.8%; category 4, 34.0%; and category 5, 15.4%. The most common histologic diagnoses of benign lesions biopsied were fibroadenoma and fibrocystic changes-proliferative and nonproliferative. The most common histologic diagnoses of malignant lesions biopsied were infiltrating ductal carcinoma and ductal carcinoma in situ. Utilization rates of the biopsy techniques varied by BIRADS category.
Conclusions: Our study revealed that BIRADS does improve the quality of the risk assessment information by making the PPV more specific to a patient's mammogram rather than simply related to an overall PPV. Our histology analysis showed category 3 and category 4 benign biopsies were predominantly because of fibrocystic changes. Category 5 lesions were predominantly invasive ductal carcinoma. Analysis of biopsy modalities indicated the preferred method for management of radiographically detected lesions evolved from stereotactic core biopsy to directional, vacuum-assisted biopsy over the course of the study.