New study finds breast cancer sometimes missed by noninvasive tests
Four common noninvasive tests for breast cancer might not be accurate enough to routinely replace biopsies for women who receive abnormal findings from a mammogram or physical examination, according to a recent study released by the
Agency for Healthcare Research and Quality
(AHRQ of Rockville, Md).
The report found that each test—MRI, ultrasonography, PET, and scintimammography—would miss a significant number of cases of cancer, when compared with immediate biopsy for women at high-enough risk to warrant evaluation of breast cancer.
"So many women today undergo biopsies only to learn they do not have breast cancer," said AHRQ Director
Carolyn M. Clancy
, MD. "Hopefully, noninvasive tests can continue to improve so that in the future, there will be a viable alternative to biopsy. But early and accurate diagnosis of breast cancer is crucial. At this time, biopsies remain the most effective technique when mammography or physical examination reveals a potential problem."
A woman receiving an abnormal mammogram or physical examination needs further confirmation to determine whether cancer is present. Confirmation currently is recommended through a tissue biopsy, either by surgical excision or needle sampling.
Statistics state that one in five women currently having biopsies for abnormal mammogram or breast examinations have breast cancer. The need for confirmation of the mammogram means some 80% of women with an abnormal mammogram must undergo the biopsy procedure, even though they ultimately prove not to have cancer. Accurate noninvasive tests could reduce the number of women that need to go under the needle.
The study, titled "AHRQ's Comparative Effectiveness Review: Effectiveness of Noninvasive Diagnostic Tests for Breast Abnormalities," indicates that the four above-mentioned tests would miss about 4% to 9% of cancer cases among women testing negative who have average risk for the disease, with potentially more missed cancers among women at high risk. Key findings include that for every 1,000 women who had a negative:
- MRI, about 962 would have avoided an unnecessary biopsy, but 38 would have missed cancers;
- PET scan, about 924 women would have avoided an unnecessary biopsy, but 76 would have missed cancers;
- scintimammogram, about 907 would have avoided an unnecessary biopsy, but 93 would have missed cancers; and
- ultrasound test, about 950 would have avoided an unnecessary biopsy, but 50 would have missed cancers.
The findings for the study were calculated based on the average risk for cancer, but the study notes that risks for individual women could vary widely, based on such factors as age, family history, and specific findings on mammograms or physical examinations. The report states that women who elect to have a noninvasive procedure should discuss their risk of cancer with their healthcare provider.
"A wealth of information in this report can give women and their healthcare providers detailed and helpful insight into the strengths and weaknesses of each of these techniques," Clancy said.
Although no accuracy rate is established as acceptable, the report cites a 2003 analysis by the Ontario Ministry of Health that concluded that an accuracy rate for negative findings of 98% or more (20 cancers missed per 1,000 women testing negative) would be an acceptable level to reliably preclude breast biopsy.
The report—which was carried out through systematic review of 81 studies by the
ECRI Evidence-Based Practice Center
(Plymouth Meeting, PA)—is available at
www.effectivehealthcare.ahrq.gov
.
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