Results of a study of nearly 300,000 Ontario women conducted by Anna Chiarelli and her colleagues found that more breast cancers were detected when clinical breast exams (CBE's) were provided to women who were undergoing mammography. In addition to finding more cancers, combining CBE with mammography produced more false positives.

Surprisingly, nearly all of the many media reports of the Cabadian study featured negative findings rather than on the result of improved cancer detection. Only one commentator observed that the critical finding in the study was improved breast cancer detection.

Related studies have found that the accuracy of mammography and CBE are significantly associated with skill of the clinician. Less skilled clinicians produce substantially higher rates of false positives and false negatives. A report in JAMA described the standards leading to CBE performance skill.

Results of the Canadian study were released on August 31, 2009) -more to follow.