From JAMA, “Breast Cancer Screening Using Tomosynthesis in Combination With Digital Mammography“:
Importance Mammography plays a key role in early breast cancer detection. Single-institution studies have shown that adding tomosynthesis to mammography increases cancer detection and reduces false-positive results.
Objective To determine if mammography combined with tomosynthesis is associated with better performance of breast screening programs in the United States.
Design, Setting, and Participants Retrospective analysis of screening performance metrics from 13 academic and nonacademic breast centers using mixed models adjusting for site as a random effect.
Exposures Period 1: digital mammography screening examinations 1 year before tomosynthesis implementation (start dates ranged from March 2010 to October 2011 through the date of tomosynthesis implementation); period 2: digital mammography plus tomosynthesis examinations from initiation of tomosynthesis screening (March 2011 to October 2012) through December 31, 2012.
Main Outcomes and Measures Recall rate for additional imaging, cancer detection rate, and positive predictive values for recall and for biopsy.
Tomosynthesis is a 3-D technique that can be added to mammograms to improve detection. At least, that was the thought. This study went back and looked.
Researchers looked at more than 450,000 exams, of which more than 173,000 were done with the addition of tomosynthesis. They found that for every 1000 digital (regular) mammograms performed, 18.1 biopsies were performed and 4.2 cases of cancer were detected. With tomosynthesis added, for every 1000 women screened, 19.3 biopsies were performed and 5.4 cases of cancer diagnosed. More invasive cancer was detected with tomosynthesis added as well.
Many will seize on this to say that we’re going to pick up more cancer with the new technology (which we will). What they might not say is that the new technology costs more, exposes women to significantly more radiation, and may lead to even more over-diagnosis. No one knows if any of this increased detection leads to more lives saved.
Just as mammography may not actually save lives, there’s a chance that 3-D might not either. It would probably be good to know that before we decide to expand the use of the technique massively.