Abstract P3-01-11: A clinical study indicates that 3D mammography shows no improvement over 2D mammography in cancer detection rates and biopsy-derived positive predictive value among BI-RADS 4 populations
Authors: Ezeana Chika Frank , Puppala Mamta , Wang Lin , Chang Jenny C. , Wong Stephen T.C. 
Published: March 2022

The Breast Imaging Reporting and Data System (BI-RADS) was developed to standardize breast imaging reporting and facilitate cancer-probability communication and biopsy decision-making. However, the probability of malignancy for BI-RADS 4 designated breast lesions ranges from 2 - 95% and contributes to a high unnecessary biopsy rate. Over the decades, BI-RADS 4 tissue biopsy-proven positive predictive value (PPV3) rate have not improved (currently 21.1%) and translates to high false-positive rates of mammography. Recent advancements in breast cancer evaluation have resulted in digital breast tomosynthesis (DBT) to generate 3D images. Objectives. 1. To investigate the clinical performance of digital mammography (2D) versus DBT (3D) among Houston Methodist's BI-RADS 4 population. 2. To compare both modalities and determine if 3D mammography performs better than 2D mammography especially per cancer detection rates (CDR) and biopsy-derived positive predictive value (PPV3) among BI-RADS 4 population in a health system in Texas. Methods. We extracted retrospective clinical and mammography data for patients who underwent screening or diagnostic examination using 2D (DM) and 3D (DBT), performed between February 1, 2015, to September 30, 2020, from our clinical data warehouse at Houston Methodist. Data elements extracted include patient demographics including age, gender, race, and marital status; mammography modality used (2D vs. 3D); personal history of breast cancer; history of prior mammogram; final BI-RADS category; biopsy type: core needle or surgical; pathology results (malignant or benign) performed within three months after the mammogram; tumor staging; and hormone receptor and growth-promoting protein expression i.e. ER, PR, and HER2 status. Using student t, Fisher's exact, and Chi-squared tests, we evaluated the collected data to determine statistical significance of the difference between modalities in BI-RADS 4 cases including malignancy rate. We calculated the adjusted odds ratio between modalities for cancer detection rate (CDR) and biopsy-derived positive predictive value (PPV3). A p-value of &lt; 0.05 was considered statistically significant. Results. A total of 158,630 encounters (83,905 unique patients) and 185,213 encounters (106,169 unique patients) had 2D and 3D mammography respectively performed across our hospital system. Out of these, 6,887 encounters (6,462 unique patients) in 2D and 6,483 encounters (6151 unique patients) in 3D were assessed as BI-RADS 4 within the period. Using Fisher’s exact test, the results show that the BI-RADS 4 assessed cases in 2D mammography are significantly more than those in 3D mammography by 24%, p-value &lt; 10e-16 (1.24; 95% CI: 1.198 - 1.284). Among the parameters, only racial distribution (P=0.0018), history of breast cancer (P=0.0030), and prior mammogram performed (p&lt;2e-16) were found to be significantly different between the modalities. The CDR among BI-RADS 4 cases were 117.47 for 2D and 122.32 for 3D with an adjusted odds ratio of 0.99 (0.89, 1.10) P=0.8725 adjusted by logistic regression. The PPV3 among BI-RADS 4 cohort were 15.09% (2D) and 16.27% (3D) and again, this difference was not significant with an adjusted odds ratio of 1.03 (0.92, 1.15), P=0.5796 adjusted by logistic regression. Conclusions. While DBT showed statistically significant improvement in performance and sensitivity in assigning BI-RADS 4 cases compared with DM i.e. 24% less assignment, there was no improvement in PPV3 and CDR in BI-RADS 4. Thus, DBT does not provide a reduction to unnecessary biopsies in BI-RADS 4 assessed patients. These findings are based on patient populations of our 9-hospital health system. Further investigation in different health systems is necessary to confirm these findings.

Citation Format: Chika Frank Ezeana, Mamta Puppala, Lin Wang, Jenny C. Chang, Stephen T.C. Wong. A clinical study indicates that 3D mammography shows no improvement over 2D mammography in cancer detection rates and biopsy-derived positive predictive value among BI-RADS 4 populations [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-01-11.