AHRQ: Noninvasive tests for breast cancer not precise enough
Such noninvasive tests as MRI, ultrasonography, PET, and scintimammography, which are commonly used to detect breast cancer, are not precise enough to regularly replace biopsies for women who are shown to have abnormal findings from a mammogram or physical exam, according to a study released recently by the Department of Health & Human Services’ Agency Healthcare Research and Quality (AHRQ).

The report finds that each of the four tests would not be able to find a considerable amount of instances of cancer when compared to immediate biopsy for women at high-enough risk.

Mammography and physical examination are both used to detect the possibility of breast cancer. The norm is for confirmation through some type of tissue biopsy.
Approximately one in five women that undergo a biopsy to investigate abnormal results from a mammogram or breast exam turns out to actually have cancer. There’s no choice but to do a follow-up exam, regardless of the fact that 80 percent of these women will turn out not to have cancer. And it’s true that accurate noninvasive tests would reduce the number of women that have to have biopsies, AHRQ said.

Disappointingly, AHRQ's review indicates that the common noninvasive tests would miss about 4 percent to 9 percent of cancer cases among women testing negative who have average risk for the disease, with potentially more missed cancers among women at higher risk, according to the study.

"So many women today undergo biopsies only to learn they do not have breast cancer. Hopefully, noninvasive tests can continue to improve so that in the future, there will be a viable alternative to biopsy," said Carolyn M. Clancy, MD, director, AHRQ. "But early and accurate diagnosis of breast cancer is crucial, and at this time, biopsies remain the most effective technique when mammography or physical examination reveals a potential problem," Clancy added.

The organization released findings for the tests reviewed:
  • MRI -- For every 1,000 women who had a negative MRI, about 962 would have avoided an unnecessary biopsy, but 38 would have missed cancers;
  • Ultrasonography -- For every 1,000 women who had a negative ultrasound test, about 950 women would have avoided an unnecessary biopsy, but 50 women would have missed cancers;
  • PET scan -- For every 1,000 women who had a negative PET scan, about 924 women would have avoided an unnecessary biopsy, but 76 women would have missed cancers;
  • Scintimammography -- For every 1,000 women who had a negative scintimammogram, about 907 women would have avoided an unnecessary biopsy, but 93 women would have missed cancers.
The findings are calculated based on average risk for cancer, but risks for individual women may vary widely. The organization recommends that women electing to have a noninvasive procedure should discuss their individual risk of cancer with their health providers.

The report was carried out through systematic review of 81 studies by the ECRI Evidence-based Practice Center, Plymouth Meeting, Pa. ECRI is one of 13 evidence-based practice centers carrying out effectiveness research for AHRQ's new Effective Health Care Program. The program compares the effectiveness of different treatments for health conditions.