A new study shows that annual mammogram screenings, combined with ultrasounds and MRIs, significantly increase the detection of cancer in women who had an elevated risk of breast cancer.
Scientists at the University of Pittsburgh School of Medicine examined data from the American College of Radiology Imaging Network trial. Their study involved about 2,700 women seen at 21 different sites. More than half of those women had a history of breast cancer themselves -- which also puts someone in the intermediate-risk category. Every year for three years, women had both a mammogram and an ultrasound to check for signs of cancer. Finally, the researchers offered participants one MRI as a final check. Over the study period, there were 111 new cases of breast cancer, 59 of which were picked up during mammography. Another 32 tumors that weren't spotted on mammograms were found with ultrasound -- 30 of which were invasive cancers. Out of 612 women who opted for MRI, nine more cancers that hadn't shown up on other screening tests were detected. Eleven cancers were diagnosed at some point during the study through means other than screening.
“For women with dense breasts who are at higher risk, cancers tend to be more advanced,” said Dr. Wendie Berg, the trial's principal investigator and professor of radiology at the University of Pittsburgh School of Medicine. “The combination of ultrasound and mammography is quite effective in finding the cancers.” The research was published Tuesday in the Journal of the American Medical Association and funded by the Avon Foundation and the National Cancer Institute.
In women with dense breast tissue who may be at higher risk of developing breast cancer, mammograms are less likely to detect the cancer, so researchers said this is where supplemental screening tools can help say researchers. Of note from the study, although more cancers were detected (adding ultrasound led to 242 patients undergoing biopsies), only 7.4 percent of these women ended up having cancer.
“While supplemental ultrasound and MRI screening detect more cancers, it is important to emphasize that an annual mammogram is still recommended and neither ultrasound nor MRI is meant to replace mammography,” said study author Ellen Mendelson, a professor of radiology at Northwestern University’s Feinberg School of Medicine, in Chicago, in a statement.
Federal guidelines currently suggest that women older than 50 receive a mammogram once every two years. But those guidelines clash with recommendations from the American College of Obstetrics and Gynecology, and the American Cancer Society. Both organizations recommend women begin getting annual mammograms at age 40. Recommendations from cancer and radiology organizations call for women who are at high risk of cancer, including those with BRCA1 and BRCA2 gene mutations, to get magnetic resonance imaging (MRI) in addition to annual mammography.
This comes in the wake of a Norwegian study published Sunday in the Archives of Internal Medicine that found that women who underwent regular mammogram screenings had an estimated 15 percent to 25 percent of breast cancers diagnosed. This could be over-diagnosis say researchers. Overdiagnosing and false-positives have long been part of the debate about breast cancer screenings, but Berg said most overdiagnosing occurs in women who have ductal carcinoma in situ, a cancer that hasn't spread past the milk ducts and is usually less severe than other forms of the disease. “Oftentimes, DCIS will never come to matter in a woman's lifetime, but we didn't look at that,” said Berg. “For these invasive cancers, it's hard to argue that they're not important because those are the ones more likely to spread and matter.”
“The fundamental problem is that we have no evidence that detecting these cancers by ultrasound actually saves lives,” said Dr. Daniel B. Kopans, a professor of radiology at Harvard Medical School. “With all the effort that has gone into ultrasound screening over the last decade, it is surprising that no one has done a randomized, controlled trial, which is the only way to know if finding these cancers actually saves lives.” The only screening tool that has been shown to reduce breast cancer death rates in the U.S. is mammograms. There has been a 30 percent decrease in deaths since 1990, Kopans said.
While Berg said that ultrasounds are cheaper and probably more readily available to more women, Kopans said “MRI has an even better chance of saving more lives. Ultrasound has shown important potential, but before the population is subjected to ultrasound screening, a randomized control trial should be done to prove its benefit,” said Kopans.
MRI has been shown to detect considerably more cancers than combined ultrasound and mammography in high-risk women, and in the main ACRIN 6666 study boosted yield by an absolute 56% compared with 34% when adding ultrasound to mammography among intermediate-to-high-risk women with dense breasts. But the clinically detected interval cancer rate was low at 8% in that study, and all were still node-negative at diagnosis. “Despite its higher sensitivity, the addition of screening MRI rather than ultrasound to mammography in broader populations of women at intermediate risk with dense breasts may not be appropriate,” Berg's group wrote, “particularly when the current high false-positive rates, cost, and reduced tolerability of MRI are considered.”
But Dr. Susan Roth, a radiologist from the Hospital of the University of Pennsylvania in Philadelphia, said the rate of false positives with ultrasound was concerning. “Even if you believe in screening ultrasound, the dilemma I have is the number of biopsies I'd have to do to find those cancers,” said Roth, who also wasn't part of the research team. Ultrasounds are time-consuming, she said, and many facilities that do cancer screening are strapped as it is. And insurance companies may not want to pay for annual ultrasounds, given how many women qualify as intermediate-risk. “The more tests you add, we'll find more cancers, and they're real,” Roth told Reuters Health. “The question is, what are we willing to pay for that, in terms of the downsides and the dollars?”
Nevertheless, Berg believes there is a place for these supplemental screenings for women at higher risk of developing breast cancer. “I don't have to be apologetic for over-screening 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,” said Berg. “This is exactly the type of cancer that is appropriate for these screening tools.”
“For high-risk women unable to undergo MRI, and for intermediate-risk women with dense breasts, including those with a personal history of breast cancer, this study supports the use of supplemental screening with ultrasound in addition to mammography,” the researchers concluded. An obstacle, though, would be that breast ultrasound is reimbursed at a rate that doesn't cover the costs of performing and interpreting thorough screening, they warned. A shortage of qualified breast ultrasound technologists is another barrier.
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