Alyssa Pollizzi and Rachel Klein
In February 2011, the FDA approved tomosynthesis as a breast cancer screening and diagnostic tool. Unlike traditional 2D mammography, DBT captures multiple images from the breast and reconstructs them to form a 3D image.
Fast forward to 2013. Clinical evidence has yet to convince the radiology community that the higher cost of the tomo system, longer radiologist read time, and additional radiation dosage is worth it. Practitioners also wonder which population this technology is best suited for - Screening? Diagnostic? Dense breasted women? A firm answer isn't available.
Funded by Hologic, the Oslo Breast Cancer Screening Trial is the first large scale (n=12,631) observational study focusing on DBT’s performance in a population-based screening setting. Research compares digital mammography alone (2D) to digital mammography in combination with DBT (2D + 3D).
DBT study shows 15% reduction in recall rate
This Norwegian study is based on 12,631 screening exams from November 2010 to December 2011. Routine craniocaudal and mediolateral oblique views were taken of each breast using 2D and the 2D + 3D mode.
Statistically significant findings of this study show that using DBT in combination with 2D mammography during screening:
- Increases detection of both invasive and in situ cancers by 27%
- Reduces false-positive rates by 15%
- Yields comparable positive predictive values (PPV) to 2D mammography alone, ~28%
- Detects 40% more (25 additional) invasive cancers than 2D mammography alone
Reading time was also found to be longer for the combination mode than 2D alone (91 seconds vs. 45 seconds on average) but the exact impact on the radiologist's workflow and efficiency was not assessed.
These results encompass a wide range of breast tissue types, from fatty to dense.
DBT may find more cancers—but questions still linger
Although radiologists spend more time reading during the upfront exam, this study implies that DBT results in fewer diagnostic workups. The study results apply to a wide range of breast tissue types, namely dense breasted women, where the overlapping layers of tissue make it difficult for 2D mammography to accurately detect microcalcifications.
The radiology community is still concerned with radiation dose, but several approaches are on the horizon for reducing dose. For example, Hologic’s C-View Software upgrade may help ease the hesitation providers feel about investing in tomo with its potential to cut dose in half.
A population based study of this size will give clinicians a better idea on how to best utilize DBT in the breast imaging pathway. The bottom line is that without securing incremental reimbursement, and possibly additional clinical evidence, it could be hard for Hologic to continue to drive sales in the U.S.
Our Take: Strategic Investment Advice from the Experts
If you’ve been considering investing in tomo, you may want to wait a little while longer because this study alone won’t be enough to crown DBT as the new gold standard in breast cancer screening.
Reducing dosage without compromising the ability to increase sensitivity and specificity over 2D will be needed to slot DBT into the breast cancer screening guidelines and secure its role in the breast imaging pathway.