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Screen Test —
MRI Auditions for Role in Breast Cancer Screening Researchers are studying costs and benefits in different patient populations to better identify when to use MRI as a screening tool. Women carrying the BRCA1 and BRCA2 gene mutations may prove to be good candidates. A screening mammogram costs less than $100. Screening for breast cancer with MRI typically costs approximately 10 times that amount. However, researchers and clinicians believe the extra cost can be well worth it for some women who are at high risk of developing breast cancer. Sylvia Plevritis, PhD, and her colleagues at the department of radiology at Stanford University School of Medicine examined the cost effectiveness of screening women with the BRCA1 and BRCA2 gene mutations with MRI. Women with these gene mutations have a higher risk of developing breast cancer during their lifetimes than the general population. In addition, BRCA1 mutation carriers’ cancers tend to be more aggressive. BRCA1, BRCA2 Mutations Elsie Levin, MD, medical director of the Faulkner-Sagoff Breast Imaging and Diagnostic Centre in Boston, believes the study only adds to the growing body of data that supports screening MRIs for women who are documented gene carriers. “We have pretty good data on this population, and I would not hesitate to recommend breast MRI to supplement mammography in women who are documented gene carriers,” Levin says. She added that she would consider screening MRI examinations for women at high risk for other reasons, including a personal or family history of breast or ovarian cancer. Breast MRI may be useful for women whose original carcinoma was not seen on mammography, Levin says. “If her original carcinoma was occult to mammography, she doesn’t get any comfort from me telling her that her mammogram looks fine,” Levin says. “She rolls her eyes and gives me a snide: ‘You didn’t see it the first time around.’ So, that’s another population I would consider screening with MR.” Handling False Positives Often, Levin says, a suspicious finding on an MRI can be followed with an ultrasound examination of the breast, which is a relatively quick and easy procedure. “If you can convert more of your positive MRIs into ultrasound biopsies that reduces the time, cost, and anxiety associated with it,” she says. For women at high risk, Levin recommends spacing mammography and MRI in six-month intervals. “If a woman had a mammography in January, I would do an MRI in July. That way it gives us a check on them twice a year,” she says. The combination of screening techniques also gives patients who are known carriers of the BRCA1 or BRCA2 gene mutation a greater sense of security. “They feel as though they are really being screened carefully,” Levin says. Some women who go through genetic counseling and test positive for BRCA1 or BRCA2 mutations will opt for a prophylactic mastectomy, while others are comfortable with more aggressive screening, Levin says. MRI should not be a replacement for mammography, Levin says. Mammography can show some very small calcifications that MRI does not, and those calcifications can be an early indication of cancer. Nor would MRI be justified for routine use in patients who simply want to avoid the compression of breast mammography, she says. The researchers at Stanford used a computer to determine whether adding breast MRI is cost effective for women of certain ages who carry BRCA1 and BRCA2 gene mutations. According to background information in the study, women who inherit mutations in the BRCA1 or BRCA2 cancer susceptibility genes have a 45% to 65% lifetime risk of developing breast cancer. That percentage compares with 13.2% of the general population. According to the Susan G. Komen Breast Cancer Foundation, inherited gene mutations account for only 5% to 10% of all cases of breast cancer. However, Plevritis says that BRCA1 and BRCA2 carriers represent a higher fraction of women who get breast cancer at younger ages. Plevritis and her colleagues designed a computer model that calculated the cost effectiveness of three approaches to breast cancer screening for this high-risk population: no screening; annual mammography from ages 25 to 69; and annual mammography for women in that age group, as well as MRI for specific age groups. The computer model followed a simulated cohort of more
than 2 million women with a genetic predisposition to breast cancer
over their lifetime, starting at the age of 25. Current screening guidelines
recommend annual mammography for high-risk women starting at the age
of 25, even though the sensitivity of mammography in this population
is low. SEER Database The researchers based utilization rates and costs of diagnostic and treatment interventions on a combination of published literature and Medicare payments for 2005. The Medicare reimbursement rates they used were $86 for bilateral mammography and $1,038 for bilateral breast MRI. “That’s not charges,” Plevritis notes. “Actual charges can be much higher.” The researchers also made certain assumptions about the accuracy of mammography and MRI, such as the size of the tumors each could detect. In addition, they assumed that if a malignancy were detected, the patients would undergo mastectomy of the affected breast and possibly the other breast as well. When to Screen “We started by asking the question: What is the cost effectiveness of adding MRI to mammography for the entire population of women ages 25 to 69 who are at high risk because they carry BRCA1 or BRCA2 genetic mutations?” Plevritis says. “Next, we looked at introducing MRI screening at different ages. So we looked at every combination of starting and stopping ages,” Plevritis says. From the available data, Plevritis and her colleagues figured that adding MRI screening would cost approximately $55,000 per quality-adjusted life-year gained for women with BRCA1 and roughly $98,000 per quality-adjusted life-year gained for women with BRCA2. They did the calculations for BRCA1 and BRCA2 separately because they have different degrees of risk of breast cancer and different tumor characteristics, Plevritis notes. They concluded that annual MRI plus mammography was not cost effective for women younger than 35, in whom breast cancers are rare, nor in women aged 55 or older, who have a shorter life expectancy and may have other health problems. However, they determined that for women aged 35 to 54, adding MRI to mammography is as cost effective as some accepted interventions. Plevritis says the conclusions of the study assumes that society considers up to $100,000 per quality-adjusted life-year gained a reasonable figure and could justify medical interventions at that threshold. “We didn’t talk about going above the $100,000 per quality-adjusted life-year saved and what would happen if a higher amount were acceptable,” she says. Possibly, she says, if society were willing to go higher, “you could have more women who could potentially benefit from MRI breast screening.” The researchers also concluded that adding MRI screening is even more effective for women who are carriers of the BRCA1 gene mutation than carriers of the BRCA2. “Because the BRCA1 population has a higher risk of breast cancer, it’s more cost effective to screen that population,” Plevritis says. “In addition, they also have more aggressive tumor types than our model predicts, but if you detect their cancers earlier, they have incrementally better survival than similar detection in the BRCA2 population.” A simple blood test can determine whether women are carriers of the gene mutations. “That’s the first step,” Plevritis says. Women who have grandmothers, mothers, and sisters who have breast cancer should talk to genetic counselors about their risk of breast cancer and whether they recommend getting tested. Plevritis adds that BRCA1 and BRCA2 are not the only possible genes with mutations, “but those are two that we know of.” Mammography’s Accuracy The Stanford study is based on annual MRI screenings. “We did run the models for different screening intervals,” Plevritis says. “We were asked by the reviewers to do that. But those results are very preliminary because the model wasn’t calibrated for other screening intervals.” Plevritis says a randomized clinical trial would be the best way to determine whether MRI screening could result in any reduction in breast cancer mortality, but no such trial is underway. “Even if a randomized clinical trial were initiated today, mortality outcomes would not be available for at least 15 years,” she says. Plevritis also notes that the study is based on film mammography and that digital mammography and other improvements in mammography could shift the results. “In the future, the adoption of digital mammography may alter the value of adding MRI screening,” she says. That’s especially true in light of a recent study that reported that digital mammography is more sensitive than film-based mammography in women who are premenopausal and those with dense breasts. The physicians believe the findings could increase the pressure on insurers to cover MRI screenings for the high-risk population, particularly those who are at high risk because they are carriers of the BRCA1 and BRCA2 gene mutations. Plevritis concludes that substantial declines in the cost of breast MRI screening are also likely to make it an acceptable value for a broader group of women. — Beth W. Orenstein is a freelance medical
writer and regular contributor to Radiology Today.
She writes from her home in Northampton, Pa.
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July
17, 2006
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