Biopsy remains the gold standard for evaluating women who have abnormal mammography findings, according to a government report that found noninvasive imaging tests such as MRI or PET less reliable.

All noninvasive tests studied - MRI, PET, scintimmamography and ultrasound - would reduce the number of needless biopsies, but all would miss a significant number of breast cancers, said the report issued today by the Agency for Healthcare Research and Quality (AHRQ).

Appropriate follow-up of abnormal findings on mammography continues to be a vexing problem because most women with abnormal findings on mammography do not have cancer, which means that the majority who undergo biopsy do not need it.

That clinical fact fueled a search for a noninvasive substitute, but the AHRQ report, which was based on a review of 81 published studies, indicates that none yet is an adequate diagnostic substitute for biopsy.

The AHRQ report estimated that 20% of women with an abnormal finding on mammography have breast cancer. Among the findings from the review:

 
• For every 1,000 women who had a negative PET scan, about 924 would have avoided an unnecessary biopsy and 76 women would have missed cancers.  
• For every 1,000 women with a negative scintimammogram, 93 women have missed cancers.  
• For every 1,000 women with negative MRI, 38 women have missed cancers.  
• For every 1,000 women with negative findings on ultrasound, 50 women would have missed cancers.

Put another way, for suspicious lesions in general PET sensitivity is 82.2% and specificity 78.3%; MRI, sensitivity 92.5% and specificity 72.4%; and for ultrasound sensitivity is 86.1% and specificity 66.4%. Sensitivity and specificity data are not available for scintimammography in all suspicious lesions.

If a less than 2% risk of having breast cancer with a negative diagnostic test is considered an acceptable level of risk for a diagnostic test to reliably preclude biopsy, none of these tests was

sufficiently accurate to replace biopsy for women at average risk of breast cancer, the report said.

Carolyn M. Clancy, M.D., AHRQ’s director, said that improvements in imaging technology may someday make these noninvasive tests reliable substitutes for biopsy - but that is not the case today. Since early and accurate diagnosis is crucial, “at this time, biopsies remain the most effective technique” following abnormal findings on mammography or physical examination.

The report noted that the studies reviewed were not perfect. “The evidence supporting our conclusions permits us to be moderately confident that publication of future studies will not overturn our findings,” it said. “Flaws in the evidence are responsible for ranking our confidence in our overall conclusion as moderate rather than strong.”

They also noted, “A limitation of the available studies is the

extremely high prevalence of breast cancer in the patients enrolled in them. This limitation reduces confidence that the results apply to all women who have suspicious mammograms.”

Primary source: Agency for Healthcare Research and Quality