MRI/Mammo Combo Spots Most Breast Tumors
Dual treatment caught almost all cancers in high-risk women
MONDAY, May 16, 2005 (HealthDay News) -- Mammography coupled with magnetic resonance imaging (MRI), conducted on an annual basis, would catch almost all tumors in women at high risk for breast cancer.
Those findings were reported online Monday by The Lancet to coincide with a presentation to the American Society of Clinical Oncology in Orlando, Fla. They echo the results of two smaller studies, one Canadian and one Dutch, that were reported in the past year.
"This is essentially a slam dunk in terms of affirmation of the MRI," said Dr. Jeffrey Weitzel, director of the clinical cancer genetics department at City of Hope Cancer Center in Duarte, Calif.
"This is another confirmatory paper demonstrating superiority of MRI over mammography. We would use both as complementary techniques," added Weitzel, who was not involved with the research.
Women at high risk for breast cancer because of an inherited susceptibility represent about 1 percent of all women with the disease, according to a Lancet editorial that accompanied the article. Some women in this group elect to have prophylactic mastectomies, which have been shown to almost eliminate the risk of developing breast cancer. Others elect close watching. For the latter strategy to be effective, however, the tumors need to be caught early, when they can still be cured.
In general, women who have a strong family history of breast cancer, as well as women who have proven BRCA1 or BRCA2 mutations, are more likely to develop tumors at a young age, when their breast tissue is more dense. Mammograms, the standard of care for women aged 40 and over, are less effective when tissue is dense.
Breast MRI, on the other hand, has a higher likelihood of detecting malignancies even when the breast tissue is dense.
The new research involved 649 women from 22 radiology and genetic centers throughout the United Kingdom who were between the ages of 35 and 49. All were considered at high risk for breast cancer either because of a family history or because they had a proven genetic mutation. Each participant was given an annual MRI and X-ray mammography for two to seven years.
Sensitivity, which refers to the probability of having a positive test when a tumor actually exists, was almost twice as high (77 percent) with the MRI compared to mammography (40 percent).
However, it was 94 percent when both methods were used together.
Specificity, which refers to the probability of a negative test when the patient is in fact cancer-free, was 93 percent for mammography, 81 percent for MRI and 77 percent with both methods.
MRI was particularly effective among carriers of the BRCA1 gene, detecting 92 percent of tumors while X-ray mammography only picked up 23 percent. The high sensitivity means women can have more confidence in negative results, Weitzel pointed out.
Mammography, on the other hand, was better at detecting ductal carcinoma in situ (DCIS) or early, noninvasive cancer.
"The MRI has a blind spot for DCIS, but mammography is pretty good, so you can cross-reference," Weitzel said.
Also encouraging was the fact that the tumors that were found tended to be small, and to not have advanced to the lymph nodes.
The study did not look at whether the combination of MRI and mammography impacted survival rates.
There are also questions that will affect how the combination could be implemented in actual practice. For one thing, cost may be a factor. While mammography is fairly cheap, breast MRIs can run about $1,000 per breast, Weitzel said.
Also, no researchers have yet looked at optimal timing for the screenings, and women need to be aware that not all breast MRI units are created equal. [The corresponding author on the study revealed that he is a director with share options at Specialty Magnetics, which is developing a specialized breast MRI system. He is also an author of a patent for breast MR image analysis.]
Although the combination may likely become the standard of care among women in the high-risk group, Weitzel cautioned them not to neglect their doctor's exam.
"The doctor is still necessary," he said.
The National Cancer Institute has more on genetic testing for breast cancer risk.