Breast-specific Gamma Imaging (BSGI) as a Complementary Imaging Tool for BI-RADS 0 and 4a Lesions on Mammography or Ultrasonography

Background: Mammography (MMG) and ultrasonography (US) have been used as standard imaging modalities for the diagnosis of breast cancer. However, several drawbacks have been attributed to these modalities. Breast-specific gamma imaging (BSGI), as a nuclear medicine imaging technique, has been introduced as a supplementary tool for diagnosing breast cancer. Objectives: This study aimed to determine whether the addition of BSGI to MMG or US interpretations could improve the diagnostic accuracy and reduce the need for further examinations or unnecessary biopsies of breast lesions. Patients and Methods: This retrospective study was conducted on 548 patients with 638 breast lesions from February 2013 to December 2018. The performance of BSGI, MMG, and US was examined for identifying breast cancer and high-risk lesions. Subgroups were classified by adding the results of BSGI for Breast Imaging-Reporting and Data System (BI-RADS) 0 and 4a lesions on MMG and BI-RADS 4a lesions on US. The diagnostic performance of each subgroup was then compared. The sensitivity, specificity, positive predictive value, and negative predictive value were also calculated. The diagnostic accuracy was determined by measuring the area under the receiver operating characteristic curve (AUC). Besides, factors associated with false-positive and false-negative results of BSGI were extracted. Results: The BSGI showed a sensitivity of 88.26% for breast cancer diagnosis, which was comparable to the sensitivity of MMG (87.95%) and lower than that of US (97.83%). The specificity and AUC of BSGI (81.62% and 0.85, respectively) were superior to those of MMG (66.83% and 0.77, respectively) and US (15.20% and 0.57, respectively). In the subgroup analysis of MMG, the sensitivity, positive predictive value, and AUC of MMG0+BSGI and MMG4a+BSGI increased significantly compared to MMG alone. In the MMG4a+BSGI group, the specificity also significantly increased. In the US subgroups, the specificity and AUC of US4a+BSGI increased significantly compared to US alone. Based on the results, a low Ki-67 index was associated with a false-negative result of BSGI. Conclusion: The addition of BSGI to MMG or US could improve the diagnostic performance, especially for BI-RADS 0 and 4a lesions. Additionally, the concomitant use of BSGI with MMG or US might reduce the need for an additional examination or unnecessary biopsy.