A new study published in The Journal of the American Medical Association found that adding tomosynthesis (also known as 3D mammography) to a digital mammogram increases the detection rate for breast cancer and decreases the number of false positives. This is good news on the false positives front but does not change the fact that the philosophy of “early detection saves lives” is fundamentally flawed, no matter what technology is used.
What we now know from a growing body of evidence is that finding more breast cancers and finding them earlier, no matter what the detection method, does not reduce the number of women who die from the disease. Breast cancer is complex and the recognition that it’s not one single disease means that the claim “early detection saves lives” has grossly exaggerated the benefits of screening. Research shows that many cancers found by using increasingly sensitive screening methods would never have become life-threatening to a woman. Other types of breast cancer are so aggressive that no matter when they are found, they are still fatal. Many of the harms of tomosynthesis continue to be the same as the harms of traditional mammography which include over-diagnosis; finding cancers that are not life-threatening and may never cause symptoms; and over-treatment – treating these over-diagnosed cancers.
As Dr. Barnett S. Kramer, director of the Division of Cancer Prevention at the National Cancer Institute states “[tomosynthsis is] not going to resolve the ongoing discussions about the overall utility of mammography.”
The specific study raises some other significant concerns. The first is that because the equipment is so expensive, breast centers that use these machines tend to serve a wealthier segment of the population, so the study’s population may not be a representative sample of women in the U.S. Second, because the study analyzed past records rather than using a more rigorous study method like a randomized controlled study, the evidence of benefit is not strong enough to encourage women and medical practitioners to add tomosynthesis to their screening regimen. Last, Hologic, the company that makes the only tomosynthesis equipment approved by the Food and Drug Administration, paid for this study and had the right to review the journal article before publication (although according to the study’s authors, they were not able to change the content). This conflict of interest should give us pause to consider who will benefit from the increase in tomosynthesis: women or Hologic?