The breast cancer screening debate continues. A new study finds that adding ultrasound or magnetic resonance imaging (MRIs) tests to annual mammogram screenings can increase cancer detection in women with higher-than-average risk of the disease.
Researchers from the American College of Radiology Imaging Network and University of Pittsburgh School of Medicine analyzed 2,809 women at a “intermediate risk” of breast cancer — women with dense breast tissue and one other risk factor, such as a personal history of breast cancer. About 2,662 women had three annual mammogram plus ultrasound screenings and, at the end of the three years, 612 also underwent an additional MRI screening.
A total of 111 breast cancer diagnoses were made. Thirty-three cancers were detected by mammograms, and another 32 were detected by ultrasound alone, nearly all of which were invasive tumors. Twenty-six cancers were found by both screens. MRI picked up an additional nine cancers that weren’t caught by mammography or ultrasound. And 11 cancers were missed by all screens, discovered when doctors or women found a lump.
“For women who have dense breasts, adding ultrasound to mammography will increase the chance of finding invasive breast cancer before it spreads to the lymph nodes,” study author Wendie Berg, a professor of radiology at the University of Pittsburgh School of Medicine, said in a statement. “MRI detected additional invasive cancers not seen on mammography or ultrasound. However, we found that MRI was significantly less tolerable than mammography or ultrasound for many study participants.”
All women had been given the choice to have an additional MRI, but only 58% of the participants chose to undergo the test, which involves being injected with special dye and then lying in the confined space of an MRI machine.
Notably, the researchers acknowledge that extra screenings also leads to an increase in false-positive results. HealthDay reported:
Berg said that ultrasound resulted in an additional 7 percent recall rate, and 5 percent of those women had to have a biopsy. Only 7 percent of the biopsies detected cancer, she said. But for MRI, the recall rate was 20 percent and 7 percent of those women needed a biopsy. Just 19 percent of these biopsies found cancer, said Berg.
The findings come on the heels of a recent Norwegian study that suggested that routine mammogram screening may overdiagnose some early cancers. The researchers estimated that between 15% and 25% of breast cancers found by mammograms would not have caused problems during a woman’s lifetime, yet are still unnecessarily still treated with surgery and chemotherapy.
Berg argues, however, that overdiagnosis occurs most often in women with ductal carcinoma in situ — a cancer that hasn’t spread past the milk ducts and can be less severe. According to Berg, the current study is still important since the researchers focused on invasive cancers, which are more likely to spread.
“I don’t have to be apologetic for overscreening when we found that 94 percent of the cancers found with these tools were invasive cancer, and 96 percent of them had not yet spread to lymph nodes,” Berg told ABC News. “This is exactly the type of cancer that is appropriate for these screening tools.”
For women at average risk of breast cancer, the U.S. Preventive Services Task Force recommends mammograms every other year between the ages of 50 and 79. However, other groups still favor more frequent screening: the American Cancer Society recommends that women over age 40 get a mammogram every year.
The study was published Tuesday in the Journal of the American Medical Association.