Health
Scanning the options: Alternatives in breast imaging technology
■ Although mammograms remain the gold standard for breast cancer screening, other techniques are aiding detection at earlier, more curable stages.
By Susan J. Landers — Posted Feb. 9, 2009
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Which screening tool for which patient? Click detail to read more about each detection technique.
When it comes to screening for breast cancer, there are choices, said Therese Bevers, MD, medical director of the Cancer Prevention Center and Prevention Outreach Programs at M.D. Anderson Cancer Center at the University of Texas in Houston.
"We have learned that one size doesn't fit all. Saying that all women should get a screening mammogram at age 40 doesn't work anymore." The trend, in her view, is moving toward personalized screening recommendations based on level of risk.
But that magic number -- age 40 -- is still the appropriate time for a woman at average risk to begin getting screened. For those at increased risk, though, earlier screening and additional imaging methodologies should be considered, Dr. Bevers said.
Magnetic resonance imaging, as well as ultrasound, now have a place in the screening picture. But which women benefit from which technique? By asking the right questions and following updated guidelines, physicians can provide direction.
The American Cancer Society now recommends more individualized advice, urging women and their physicians to discuss the possibility of beginning screening earlier, at age 30, or in rare cases even younger, depending on family history.
For example, women treated with chest radiation for a pediatric malignancy face a significantly increased risk of breast cancer at a young age. By age 45, it is estimated that from 12% to 20% of women treated with moderate- to high-dose radiation when they were children will be diagnosed with breast cancer, according to a study in the Jan. 28 Journal of the American Medical Association.
It is these women who should begin screening tests early -- at age 25 or eight years after radiation, whichever occurred later, according to the study in JAMA.
The cancer society recently added MRIs to its guidelines. Data have been building that show the additional detection power generated by a magnetic field.
Ultrasound continues to hold its own as an important tool, too. It provides an extra measure of detection for women with dense breasts. Its use in this manner gained attention as a result of a study published last year in JAMA.
But just as screening options are expanding, the number of women having mammograms has begun to decline. Mammogram rates were steadily increasing among women age 40 and older until 2000. Then the rates stabilized and began to drop, according to a 2007 update of the National Cancer Institute's Cancer Trends Progress Report. And no one has a clear answer as to why.
After non-melanoma skin cancer, breast cancer is the most common form of cancer in women, according to the Centers for Disease Control and Prevention. In 2004, more than 186,000 women were diagnosed with it, and nearly 41,000 died, according to CDC figures.
Reversing that downward mammogram trend will be crucial in reducing the odds that more women will die from their disease.
"There is no known cause, so we are all at risk," said Linda Aboody, MD, director of radiology at Memorial Sloan-Kettering Cancer Center in Basking Ridge, N.J.
Early detection is an all-important, life-or-death factor. And physicians play a significant role in starting the process.
"It makes a huge difference when their doctors tell [patients] to get screened," said Debbie Saslow, PhD, director of breast and gynecologic cancers for the ACS.
ADDITIONAL INFORMATION
Mammograms
![[Mammogram]](/amednews/2009/images/phlsa0209c.jpg)
For most women older than 40 and at average risk for breast cancer, the traditional mammogram is recognized as the gold standard. Its use is supported by all physician organizations, including the AMA. Annual mammograms have been shown to significantly reduce deaths among women in this age group.
In fine-tuning the mammogram recommendation, physicians and their patients should be aware of the recent addition of digital mammography to the traditional film image option. What makes digital mammography different is that it is read on a computer, Dr. Bevers explained. Many facilities are gradually replacing their analog machines with digital machines, but the digital machines are much more expensive, she noted.
Many reasons show the added cost may be worthwhile. For instance, viewing the image on a computer enables a radiologist to alter contrast and enhance the picture to make it easier to identify subtle differences in tissue. Also, digital screening has demonstrated an advantage in imaging dense breasts. Saslow noted that digital mammography was determined in some studies to provide a clearer image for younger, premenopausal women whose breasts generally are denser than are older women's. Digital machines also could help in rural locations or other areas in which the images need to be sent to another site for reading by more experienced radiologists.
But one clear benefit to digital images is the ability to quickly retrieve previous scans, said Douglas Yee, MD, director of the Masonic Cancer Center at the University of Minnesota. "That's hugely important," he said. "Often the mammographers want to look at something over time."
With film, women must be sure to bring previous films with them if they move to a new facility, Dr. Aboody said.
She cautions that women and their physicians should not select a screening site solely because a digital machine is available. The more important criterion is that the facility meet the Mammography Quality Standards Act of 1992, which defines minimal requirements for radiation dose, image quality, radiologist training and continuing education.
![[Ultrasound]](/amednews/2009/images/phlsa0209d.jpg)
Ultrasound
Ultrasound has long been used to evaluate abnormalities found during mammography or a clinical breast exam, but a recent JAMA study found its use led to cancer detection among women who were at increased risk of the disease.
The finding was particularly true for women with dense breast tissue.
The study is part of the American College of Radiology Imaging Network, or ACRIN, trial. The researchers found that adding a single screening ultrasound to mammography yielded an additional 1.1 to 7.2 cancers per 1,000 high-risk women.
Among the criteria for determining high risk were personal history of breast cancer, prior atypical biopsy and elevated risk determined by commonly used risk calculation models -- the Gail or Claus models.
The downside of ultrasound is the high number of false-positives and the need for unnecessary biopsies and/or follow-up, researchers noted. The study is ongoing. "The difficulty ... is the very high biopsy rate that results from it, and the relative lack of availability of high-quality ultrasound screening," Dr. Aboody said. "For both these reasons, ultrasound screening will remain controversial, but new data now support some efficacy."
The ACRIN findings, which were released in May 2008 as were the National Comprehensive Cancer Network's guidelines, include "preliminary data," said Dr. Bevers, who chaired the panel that drafted the guidelines. Although not yet a first-line screening tool, "I might try ultrasound for women who are claustrophobic or too big to fit into the MRI machine."
![[MRI]](/amednews/2009/images/phlsa0209e.jpg)
Magnetic resonance imaging
MRI is the gorilla in the room. It is emerging as the most promising new screening technique -- and the most expensive. "MRI is the most exciting thing in breast imaging," Dr. Aboody said. "It's an extremely powerful tool and has been called a monster to be tamed."
The device has a high sensitivity for invasive cancer, the most dangerous type, and can find very small lesions that aren't seen on mammograms or ultrasound exams, she added. But it may also miss some cancers, which mammography is better at detecting, she added. Plus, it produces many false-positive results.
The ACS released new guidelines in 2007 calling for the use of both mammography and MRIs for women at increased risk for breast cancer. The society now recommends the two for women who have a 20% to 25% or greater lifetime risk of the disease.
The NCCN guidelines call for annual MRIs and mammograms, and a clinical breast exam every six months to a year for women 25 and older who have a strong family history or other genetic predisposition for breast cancer.
When determining a woman's risk and the need for screening with an MRI, the ACS considers whether a woman has a BRCA1 or BRCA2 mutation. Other factors include whether she has a first-degree relative with a mutation; a lifetime risk of breast cancer of 20% or higher using standard risk assessment models; or if she received radiation to the chest between ages 10 and 30 for treatment of, for example, Hodgkin's disease. Another important variable is whether the woman carries a genetic mutation in the TP53 or PTEN genes, or has a first-degree relative who carries the mutation.
But many of these high-risk women do not receive appropriate screening, according to a study in the Jan. 28 JAMA. Researchers found that of the 625 women studied, many had never received a mammogram despite having had chest radiation therapy when they were children.
In addition, several other groups require individual assessment as to whether MRIs are appropriate. They include those who have had breast cancer, carcinoma in situ or atypical hyperplasia, or have extremely dense breasts.
"As with other cancer screening tests, MRI is not perfect and in fact leads to many more false-positive results than mammography," said Christy Russell, MD. She served as chair of the ACS Breast Cancer Advisory Group and is the co-director of the University of Southern California/Norris Breast Center in Los Angeles.
"Those false-positives, which can lead to a high number of avoidable biopsies, can create fear, anxiety and adverse health effects, making it imperative to carefully select those women who should be screened using this technology," she said.
