Last Updated: 2011-04-05 15:27:05 -0400 (Reuters Health)
[Clarifies findings in paras 1 and 2 of story posted Apr 5, 2011 as 20110405elin002.]
By Amy Norton
NEW YORK (Reuters Health) - Breast cancer screening that includes MRI scans might help find cancers at an earlier stage in high-risk women, reducing the likelihood that the tumors will become advanced before they're diagnosed, a new study suggests.
Whether discovering tumors earlier means women at high genetic risk for breast cancer will live longer isn't clear yet, however.
"I think the main take-home message for women is that there are choices, and we have data to support them," said Dr. Monika L. Burness of the University of Chicago in Illinois, who co-authored an editorial published with the study.
The study, reported in the Journal of Clinical Oncology, followed women with mutations in the BRCA1 or BRCA2 genes that put them at a much higher than average risk of developing breast or ovarian cancer.
The National Cancer Institute estimates that about 60 of every 100 women with these gene mutations will develop breast cancer over their lifetime - versus around 12 of every 100 women in the general population.
For women at average risk of breast cancer, experts recommend breast cancer screening with mammograms. But because MRI can pick up smaller tumors, the American Cancer Society advises that women with BRCA mutations be screened with both mammography and MRI.
Until now, though, it had not been clear whether MRI can reduce their risk of being diagnosed with advanced cancer.
The new study looked at how far advanced the breast tumors were when they were discovered.
About a third of the women had yearly breast cancer screening that included MRI scans. Two of every 100 women in this group were diagnosed with stage 2 to stage 4 breast cancer. In the remaining two-thirds of the study participants, who had mammograms but not MRI, such higher-stage tumors were discovered in 7 of every 100 women.
In stage 2 breast cancer, the tumor is either relatively large or has spread to nearby lymph nodes; by stage 4, the cancer has spread to distant sites in the body.
Yearly screening is not the only way for women with BRCA mutations to manage their increased risk. They can also have preventive mastectomy -- surgical removal of healthy breasts -- to cut their odds of breast cancer. Two drugs, tamoxifen and raloxifene, may also be able to reduce the risk.
A study published last year in the Journal of the American Medical Association found that of nearly 2,500 women with BRCA mutations, no one who had a preventive mastectomy developed breast cancer in the next three years, compared to 7 of every 100 women who did not have the surgery.
While MRI often finds breast cancers earlier, when they're curable, according to editorial author Burness, it's not clear exactly how MRI screening measures up against preventive mastectomy in the long term.
However, she told Reuters Health, the current findings underscore the fact that women with BRCA mutations have options for managing their risk. And screening with MRI is "a reasonable alternative to preventive surgery," Burness said.
For the study, researchers led by Dr. Steven Narod of the Women's College Research Institute in Toronto, Canada, compared two different research groups.
One included 445 women with BRCA mutations who were recruited for an MRI study at the University of Toronto between 1997 and 2007. The women underwent yearly screening with MRI, mammograms, and breast exams in a doctor's office or clinic.
The other group included 830 BRCA-mutation carriers involved in a study at 13 North American medical centers. Those women were advised to undergo yearly mammograms and clinical breast exams - although no screening regimen was formally set.
The women ranged in age from 25 to 65; the average woman was in her mid-40s.
Overall, the same proportion of women -- 9 of every 100 -- in each group developed breast cancer during the 6-year study.
But women in the MRI screening group were more likely to have an early-stage cancer discovered. For example, 14 of every 100 women in the MRI group were diagnosed with early breast cancer, compared to only 7 of every 100 in the comparison group.
In contrast, only 2 of every 100 women in the MRI group received a diagnosis of stage 2 to stage 4 breast cancer, compared to 7 of 100 in the comparison group.
When the research team took some other risk factors into account -- such as age, oral contraceptive use, whether the women still had their ovaries, and other personal characteristics - they found that women in the MRI group were 70 percent less likely to be diagnosed with stage 2 to stage 4 cancer versus women in the comparison group.
Whether MRI screening actually saves lives is not yet known, however. Further studies are needed to look at its effects on death rates from breast cancer, according to the research team.
MRI screening is not without its downsides. Along with its greater sensitivity for spotting small tumors comes a higher risk of false-positives - suspicious findings that turn out not to be cancer upon further testing. That leads to unnecessary follow-up biopsies, added costs and, for some women, anxiety.
One study found that 8 of every 10 positive findings on MRI screening were actually false-positives.
MRIs are also much more expensive than mammograms, at $1,000 or more per test. For women with BRCA mutations, insurance generally covers the costs, but preventive mastectomy is less expensive. The surgery is done only once, whereas MRIs need to be repeated every year.
What it comes down to, according to Burness, is that women with BRCA mutations should be aware of all their options and discuss them with their doctor.
"In my mind," she said, "that's very empowering."
SOURCE: http://bit.ly/gF60iE Journal of Clinical Oncology, online March 28, 2011.
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