Study: MRIs find more tumors than mammograms
July 29 2004 11:00 PM ET
In women at high risk of breast cancer, new research suggests that magnetic resonance imaging scans find nearly twice as many tumors as mammograms do, but they're costly and trigger more unneeded biopsies. Ordinary mammograms are still recommended for screening most women, starting at age 50. But the benefit of better detection from MRI may outweigh its drawbacks for those with a strong family history of breast cancer or faulty genes. MRI also may make monitoring a less dangerous option for women who choose it instead of having their healthy breasts and ovaries removed as a preventive measure.
The value of mammograms for women at average risk of breast cancer has been hotly debated, though most doctors agree that the test saves lives in women over 50. The new study involved women with a higher-than-average risk, such as those with a faulty gene or a mother or sister who had breast cancer. For them, screening is less controversial. Researchers studied 1,909 Dutch women, including 358 with one of the BRCA genes or other mutations that predispose women to breast cancer. Up to half of such women get it by the time they're 50, and they are also prone to ovarian cancer. They can cut their risk of cancer and death by having their breasts or ovaries removed or by taking estrogen-blocking drugs. But many don't want such drastic measures, and researchers wanted to see if intensive screening could help such women by finding tumors early, when they're most treatable.
Researchers compared mammograms, which are breast X-rays, to MRI scans, which use magnets to make detailed images without radiation. An MRI scan costs $700 to $1,000--about 10 times the cost of a mammogram. Many large insurers already cover MRIs for women at high risk. Women were screened three ways: a breast exam by a doctor every six months, annual mammograms, and annual MRI scans. Results were analyzed by different doctors, so none knew what the others had found.
After an average of nearly three years 51 breast cancers had been identified. Some results were excluded for various reasons. Of the remaining 45 tumors, 32 were identified by MRI, including 22 that hadn't been visible on mammograms. Only 18 of the 45 tumors were caught by mammograms, a lower rate than studies typically show, some experts noted. In the United States mammography is thought to miss 15% to 25% of cases.
But MRI also gave more false alarms than mammograms. "MRI led to twice as many unneeded additional examinations as did mammography (420 versus 207) and three times as many unneeded biopsies (24 versus. 7)," the authors reported. Nevertheless, the researchers say the study clearly shows that women at high risk for breast cancer should receive MRI scans in addition to mammograms to help detect breast cancer at its earliest and most treatable stages. "Our study firmly establishes the value of screening for women with inherited predisposition for breast cancer, provided that MRI is added to mammography," said lead researcher Jan G.M. Klijn of Erasmus Medical Center-Daniel den Hoed Cancer Center in Rotterdam.
Breast cancer is the most common cancer in American women after skin cancer. About 216,000 new cases will be diagnosed this year, and it will cause about 40,000 deaths. (AP)