In a recent article in the Journal of the American Medical Association (click for abstract; Dr. Stark can, upon request, send the entire article) Rafferty and colleagues from Mass General reviewed their experience with adding tomosynthesis to conventional digital mammography, the kind of study done at most mammography centers in the U.S. Tomosynthesis is a modified CT scan, wherein several images of the breast are taken and a computer constructs a series of virtual slices, in which the radiologist can see detail that would otherwise be obscured with overlapping shadows. They, together with colleagues from Yale, U.Penn and Albert Einstein (Yeshiva U.) looked back at almost a half million studies, of which about 40% included tomosynthesis; the others did not. They found two things: there was about a 30% increased rate of diagnosing breast cancer (from 3 per 1000 to about 4) and a reduction in “call back” requests. Those are when women are told that their mammogram was suggestively suspicious but that more images are needed. Most call backs don’t result in a diagnosis of cancer, but increase anxiety among already anxious women.
This is an important study because of its size in cementing tomosynthesis as a valuable screening tool. Its major limitation is that it was not a prospective randomized trial, but rather a look back at data that had been collected in a somewhat haphazard fashion. In addition, 3D mammography has been developed since tomosynthesis became widely available; whether it will make this entire discussion obsolete is not clear yet. Nonetheless, the vast majority of mammograms are normal, and the vast majority of abnormal mammograms do not result in a diagnosis of breast cancer, so there is still much work to be done to try to make breast cancer screening more accurate. Dr. Stark’s comment: “This is an important trial. Dr. Welch and colleagues from Dartmouth would have you believe that we are overly zealous in doing mammograms, that the improvement in outcome is outweighed by many women being overtreated. Certainly better screening devices have the potential to make this dispute moot.”