Evaluating the Efficacy of 6-Month Follow-Up for BI-RADS 3 Lesions Identified by Screening Ultrasound: A Retrospective Study

Abstract

Background: The Breast Imaging-Reporting and Data System (BI-RADS), developed to standardize mammographic findings, categorizes 'probably benign' lesions as BI-RADS 3, aiming to reduce unnecessary biopsies from false positives, with a cancer likelihood of less than 2%. In some countries, screening programs have been expanded to include ultrasound alongside mammography, particularly in populations with predominantly dense breast tissue, leading to an increased detection of BI-RADS 3 lesions through this additional modality. This study examines the effectiveness of 6-month follow-ups for these ultrasound-identified BI-RADS 3 lesions. The purpose is to evaluate cancer detection rates and diagnostic performance of ultrasound findings leading to decision for biopsy. Materials and Methods: We retrospectively analyzed 7,577 women who underwent mammography and ultrasound screening from January 2016 to December 2021. Of these, 2,907 were classified as BI-RADS 3 based on ultrasound findings. The study focused on 1,163 patients with normal mammography and assessed BI-RADS 3 from ultrasound findings, who completed a 24-month follow-up. Data analysis included assessing demographic data, breast cancer risk, imaging features, and pathological findings. Results: Among the 1,163 patients, the cancer detection of the entire cohort was 0.7%, with no cancers detected during the first six months. The cancer found at 6 months and 12-24 months were 0 and 0.17%, respectively (p<0.001). The median time to be reassesed from BI-RADS 3 to BI-RADS 4 was 18.4 months. Upon the change of BI-RADS, spiculation and angular margins were the most predictive ultrasound features for malignancy (AUROC=0.75 and 0.69, respectively). Lesion size growth alone was found insufficient as a biopsy criterion. A 28% growth cutoff distinguished between benign and malignant lesions better than 20% cutoff (AUROC=0.68 vs 0.64, p=0.038). Conclusion: A 12-month follow-up interval may be more appropriate than the traditional 6-month interval for average-risk patients with BI-RADS 3 lesions detected by screening ultrasound. Combining suspicious imaging features with size increases enhances diagnostic accuracy, proposing a tailored follow-up approach based on individual risk profiles and imaging characteristics.