Combining clinical breast examinations with mammograms can sometimes catch breast cancers that mammograms alone may have missed. But it also results in a large number of wrong diagnoses, a new Canadian study finds.
The study, published online Monday in the Journal of the National Cancer Institute, found that for every extra case of cancer found by combining breast exams with mammograms, 55 women had to undergo false alarms that resulted in extra worry and uncomfortable followup testing.
Researchers have long debated whether having doctors perform breast exams on women who already have annual mammograms helps to catch more cancer cases.
For the study, researchers from the University of Toronto led by Cancer Care Ontario's Anna M. Chiarelli looked at the results of more than 290,000 women who took part in the Ontario Breast Screening Program between January 2002 and December 2003. Some went to facilities that performed only mammograms, while others went to health centres that performed both mammograms and clinical breast exams by specially trained, experienced nurses.
The researchers found that women who went to centres that offered the combination of clinical exams and mammograms were more likely to be referred for follow-up care. However, women screened at those centres also had a higher false-positive rate than women screened at centres that offered only mammography.
For every 10,000 women screened, adding the breast exams uncovered cancer in four women whose cancer would have been missed by a mammogram. But at the same time 219 women without cancer would also receive false-positive results. That works out to 55 false alarms for each additional cancer detected.
The authors note the benefits of adding clinical breast examination must be weighed against potential risks and costs that can come from false-positive results.
Those risks and costs include having women undergo unnecessary and painful biopsies, which can leave scarring, not to mention be traumatizing to patients who may need to wait weeks for results.
"More answers are needed on the role of [clinical breast examination] in breast cancer screening before definitive recommendations for or against its use can be made," write Dr. Mary B. Barton, of the Agency for Healthcare Research and Quality in Rockville, Md., and Dr. Joann G. Elmore, of the University of Washington School of Medicine in Seattle in an accompanying editorial.
"While we wait for those answers, the data presented by Chiarelli et al. suggest that [clinical breast examination] must be done well if it is to be done at all, with the acknowledgment that overall referrals and false-positive results will increase."
The study authors say they still don't have enough information to say whether clinical exams should be abandoned. But the editorialists suggest that women undergoing testing need to be better informed about the risk for false-positives from breast exams and the differences in the screening methods.
