Women who face a high risk of breast cancer should undergo annual magnetic resonance imaging to detect the disease in addition to conventional mammograms, the American Cancer Society will announce today, marking the first time that leading radiologists have advocated the routine use of MRI scans as a screening test.
The influential guidelines are aimed at the roughly 1 to 2 percent of women whose family history gives them at least a 20 percent chance of developing breast cancer during their lives. However, they are the latest evidence that MRI, which is highly sensitive but costs 10 times more than mammography, is emerging as the gold standard for finding cancer.
A related study also being released today found that, in 969 women recently diagnosed with cancer in one breast, MRI found 30 additional tumors in the opposite breast that had been missed by mammograms and physical exams.
"If my wife was diagnosed with breast cancer, I'd be sure that she got an MRI of the opposite breast," said Constantine Gatsonis , a biostatistician at Brown University who coauthored the study in today's New England Journal of Medicine.
Many radiologists have been reluctant to use MRI scans for routine cancer screening, because of their cost and because MRIs frequently show suspicious spots that, once a tissue sample is collected through minor surgery, turn out not to be cancer. However, for women with close relatives who had breast or ovarian cancer, or who have one of the so-called breast cancer genes, the Cancer Society said studies increasingly show that the benefits outweigh the cost as well as the distress of cancer "false alarms."
"A number of studies showed the addition of MRI more than doubled the screening test sensitivity," allowing doctors to detect more tumors earlier, said Robert Smith , director of cancer screening at the Cancer Society and one of 12 coauthors of the guidelines. "We felt comfortable recommending MRI for women who are at high risk."
Unfortunately, there is no easy way for many women to determine on their own whether they are in the high-risk group, the size of which is also uncertain. Women can get blood tests to find known cancer genes, including the BRCA1 or BRCA2 mutations, whose carriers face a lifetime cancer risk of up to 65 percent. But researchers believe there are others that have not yet been confirmed. As a result, doctors must estimate women's cancer risk through a detailed review of their family medical history.
"There are women who are unaware they are at high risk because they don't have obvious family history," said Smith. "It takes a genetic counselor to tease out the risk."
He said women should check with their doctor to learn their risk level.
Breast cancer advocates applauded the Cancer Society's new guidelines, which are closely followed by the radiologists who analyze breast images as well as the insurance companies that pay much of the tab. Already, some private insurers such as Blue Cross and Blue Shield of Massachusetts pay for annual MRIs for women at high risk of breast cancer, but many women don't have ready access to an MRI for breast cancer screening.
Only about 12 percent of practices that perform breast cancer imaging use MRI machines for screening, according to a survey by the Society of Breast Imaging, and half do not even have MRI machines. Women can be sent to general MRI centers for breast images, but cancer specialists say that has limited value because most are not equipped to do MRI-guided biopsies of potential tumors.
"This is a promising and important step in the right direction for screening," said Dr. Cheryl Perkins , senior clinical adviser to Susan G. Komen for the Cure , a breast cancer advocacy group based in Dallas. However, she cautioned that the increasing use of MRIs brings with it "layers upon layers of access issues" because of the lack of MRI availability or insurance coverage or because women are unaware that they should get an MRI.
"If we have the cure for cancer or a screening tool that is 100 percent accurate, it's still not going to do any good if the patients can't get to it," Perkins said.
Currently, the Cancer Society recommends that women over age 40 get an annual mammogram, and society officials stressed yesterday that there is no reason for the vast majority of women to change that practice. In an editorial in the New England Journal, Smith wrote that the death rate from breast cancer dropped 24 percent from 1989 to 2003, in part because of the widespread use of mammograms.
But at least six studies since the mid-1990s have shown that MRIs find substantially more tumors than mammograms, especially at their earliest, most treatable stage. For instance, a four-year study of 1,909 women in the Netherlands showed that MRI detected 80 percent of tumors compared with 33 percent detected by mammograms.
As a result, Cancer Society officials wanted to strengthen its 2003 recommendation that MRI "might" be beneficial for some high-risk women.
In addition, the study in today's New England Journal found that women recently diagnosed with cancer in one breast should immediately get an MRI of the other breast. Up to 10 percent of breast cancer patients eventually suffer a recurrence in the other breast, but mammograms often miss small tumors, the researchers from the American College of Radiology Imaging Network found, while MRIs rarely miss them.
However, magnetic resonance imaging has its drawbacks, including a higher rate of "false alarm." More than 1 out of 50 women in the Dutch study underwent the discomfort and psychological distress of biopsies for spots that looked potentially cancerous when the tissue turned out to be healthy. Mammograms triggered less than half as many false alarms. MRI scans also are costly: Medicare typically pays about $850 for an MRI compared with $85 for an X-ray mammogram or $135 for a digital mammogram, according to the American College of Radiology.
In addition, Cancer Society officials noted that there is no proof yet that all the extra cancers detected by MRI translate into longer lives for patients. The life-extending benefits, they said, will only become clear if women are followed over a longer time.
Ultimately, Cancer Society panelists said they did not have enough evidence to recommend annual MRIs for women who face less than a 15 percent risk of breast cancer, such as women whose breast tissue is so dense that tumors don't show up readily on mammograms and even some women who have experienced certain types of breast cancer, such as ductal carcinoma.
Dr. Daniel Kopans , a radiologist at Massachusetts General Hospital, said studies of MRI's usefulness in the broader population are urgently needed.
"The real question . . . is whether we should be screening all women with MRI," said Kopans, noting that nobody knows how many of the 40,910 breast cancer deaths expected this year in the United States could be prevented with MRI. "What if MR screening could knock it down by 90 percent? Is that worth $800 apiece to do MR screening for everyone? These are very important questions, and somebody is going to have to bite the bullet and do a very large, expensive study" to find out.
Scott Allen can be reached at email@example.com.
(Correction: Because of a reporting error, a Page One story yesterday misrepresented the American Cancer Society's recommendation for breast scans for women at high risk of breast cancer. The organization recommends that women at significantly elevated risk get both annual mammograms and annual magnetic resonance imaging scans.)