The technologies used to screen for breast cancer have changed over the past decade. While the mammogram remains the foundation of breast cancer detection, newer variations on the test may improve its ability to detect cancer.
In the late 1960’s, the modern-day film mammogram was invented and x-ray units dedicated to breast imaging became available. In 1976, the American Cancer Society recommended mammography as a screening tool. In 2000, the FDA approved the first digital mammography system. This allowed images to be stored directly onto a computer where they could be enlarged, lightened or darkened for better results. Many experts believe that for certain women, for example those with dense breasts, digital mammography is better at finding cancer than the original film mammography. But challenges still remain with mammography. The captured image, whether on film or digital, is a flat 2 dimensional (2D) end product. Yet our bodies are 3 dimensional (3D), and it stands to reason that a 3D view of the breast that can provide a more complete view may uncover cancers hidden in 2D images.
That was the thinking of Daniel B. Kopans, MD at Massachusetts General Hospital. He spent close to 15 years studying tomosynthesis, a technique that allowed x-ray images taken from different dimensions. In 1996, Mass. General filed a patent for “Tomosynthesis System for Breast Imaging” and 3D mammography was born. In 2011 the FDA approved this 3D tomosynthesis technology.
The use of tomosynthesis has gained momentum across the country and in Canada, and now the National Cancer Institute (NCI) has funded a trial that compares tomosynthesis 3D mammograms with standard 2D digital mammograms.
The Tomosynthesis Mammographic Imaging Screening Trial, or TMIST, will be the first large randomized clinical trial of screening mammography in decades and the first to compare the current standard 2D against 3D mammography. The trial is expected to eventually enroll 165,000 women between the ages of 45 and 74 in 100 sites in the United States and Canada.
The study’s principal investigator, Etta Pisano, MD of Beth Israel Deaconess Medical Center in Boston, notes that the goal of the trial is to see whether tomosynthesis has a meaningful impact on the detection of potentially life-threatening breast cancers. We know we need screening, we have the technology, but understanding whether the technology is actually benefitting women is still an unknown. Will we see a reduction in the incidence of life threatening breast cancers and hence a reduction in the rate of advanced cancers? Will we discover that we are finding too much, the dreaded false positive?
Barry Kramer, MD, MPH director of NCI’s Division of Cancer Prevention, commented, “The trial should also help to identify whether screening with tomosynthesis increases the over-diagnosis of breast cancer and to what degree.” Currently, tomosynthesis is more expensive than 2D mamography so many insurers have not embraced the technology. Maybe this trial is just what we need to answer some key questions. In the end, the ability for the patient and the physician to make an informed decision based on the results of the trial is what really matters.