Breast cancer is the most common type of cancer in women worldwide. The National Cancer Institute (NIH) estimates that there will be 232,670 new female and 2,360 new male cases of breast cancer in the U.S. in 2014. If abnormal breast tissue or cancer is found early, it may be easier to treat because the cancer may have begun to spread beyond the breast by the time symptoms appear.
While mammography—two-dimensional X-ray images of the breast—has been used for breast cancer screening since 1969, it still has potential limitations, including false-positive results, overdiagnosis and overtreatment, false-negative results, and radiation exposure.
3D Imaging Is More Effective Than 2D
In a study led by Dr. Sarah M. Friedwald of Advocate Lutheran General Hospital in Park Ridge, Ill., data from 13 centers were analyzed to determine if adding tomosynthesis, a three-dimensional breast imaging technique, to digital mammography improves breast cancer screening results.
Among the measured outcomes was recall rate, or the proportion of patients who require additional scans based on the first screening result. The researchers found an overall decrease in recall rate with mammography and tomosynthesis, as opposed to mammography alone.
Another outcome was the proportion of patients undergoing biopsies who were later diagnosed as having breast cancer. The rate was 18.1 per 1,000 screenings with mammography alone, versus 19.3 per 1,000 with digital mammography and tomosynthesis. So fewer women received unnecessary breast biopsies with the combination screening test.
For cancer detection, the results were 4.2 diagnoses per 1,000 screenings with digital mammography, versus 5.4 per 1,000 with the combination treatment. For invasive cancer, the rate increased from 2.9 diagnoses per 1,000 scans with digital mammography to 4.1 per 1,000 with digital mammography plus tomosynthesis.
The study authors wrote, “The association with fewer unnecessary tests and biopsies, with a simultaneous increase in cancer detection rates, would support the potential benefits of tomosynthesis as a tool for screening. However, assessment for a benefit in clinical outcomes is needed.”
The Experts Weigh In
In an editorial accompanying the study in the Journal of the American Medical Association, Dr. Etta D. Pisano of the Medical University of South Carolina and Martin J. Yaffe, Ph.D., of the University of Toronto, noted that while “tomosynthesis is likely an advance over digital mammography for breast cancer screening, fundamental questions about screening remain.”
Dr. Otis W. Brawley, chief medical officer of the American Cancer Society (ACS), agrees with the need for more research. “A large phase III study is the only way to determine if 3D [screening] is better than digital,” he told Healthline. “One cannot rely simply on finding cancer, as 3D may find more indolent cancers that do not need therapy.”
Pisano and Yaffe also wrote, “The time is now for the NIH to fund such a much needed trial to address many of the remaining issues about breast cancer screening.”
However, Brawley said, “NIH is not funding big long-term studies due to fiscal restraints. I do not see such a study being done; and if it were done, it’s a 15- to 20-year study [involving more than 20,000 people].”
Avoiding Unnecessary Breast Biopsies
In a separate study, published in Clinical Cancer Research, a journal of the American Association for Cancer Research, Austrian scientists determined that using four approaches together when imaging breast tumors can more accurately distinguish malignant from benign tumors than using fewer approaches. “Therefore, unnecessary breast biopsies can be avoided,” said Dr. Katja Pinker, an associate professor of radiology at the Medical University of Vienna in Austria, in a press statement.
The new imaging technique, called multiparametric (MP) 18FDG PET-MRI, was 96 percent accurate and provided better results than combinations of two or three imaging approaches. The authors estimates that this technique “can reduce unnecessary breast biopsies recommended by the commonly used imaging method, the DCE-MRI, by 50 percent.”
Pinker noted in the press statement that performing a combined PET-MRI scan is currently more cost-effective than existing breast imaging methods. "However, simultaneous PET-MRI scanners have been developed and are now being installed worldwide," Pinker told Healthline. "The use of one PET-MRI machine instead of two machines—a PET-CT and an MRI—will improve cost-effectiveness. In addition, in the current study, there was already a significant reduction in unnecessary breast biopsies with PET-MRI, which will further improve the cost-effectiveness.”
Are These Scans Safe?
Acknowledging that a PET scan might reduce costs by reducing biopsies, Brawley cautioned, “It might have serious adverse consequences. An added issue needing to be considered is that PET involves injection of a radioactive drug, which I would not want to give every year or two for a long time. We don't have long-term safety studies with PET used that way.”
When asked about the next step for reducing unnecessary biopsies, Pinker told Healthline, “We are conducting a follow-up study to confirm the results...with larger patient numbers and patients with a benign result with multiparametric PET-MRI, who are no longer subjected to breast biopsy but are followed for a time-span of at least two years to rule out malignancy.”