The contribution of clinical breast examination to the accuracy of breast screening.
BACKGROUND
There is controversy about whether adding clinical breast examination (CBE) to mammography improves the accuracy of breast screening. We compared the accuracy of screening among centers that offered CBE in addition to mammography with that among centers that offered only mammography.


METHODS
The cohort included 290 230 women aged 50-69 years who were screened at regional cancer centers or affiliated centers within the Ontario Breast Screening Program between January 1, 2002, and December 31, 2003, and were followed up for 12 months. The regional cancer centers offer screening mammography and CBE performed by a nurse. All affiliated centers provide mammography but not all provide CBE. Performance measures for 232 515 women who were screened by mammography and CBE at the nine regional cancer centers or 59 affiliated centers that provided CBE were compared with those for 57 715 women who were screened by mammography alone at 34 affiliated centers that did not provide CBE.


RESULTS
Sensitivity of referrals was higher for women who were screened at regional cancer centers or affiliated centers that offered CBE in addition to mammography than for women screened at affiliated centers that did not offer CBE (initial screen: 94.9% and 94.6%, respectively, vs 88.6%; subsequent screen: 94.9% and 91.7%, respectively, vs 85.3%). Mammography sensitivity was similar between centers that offered CBE and those that did not. However, women without cancer who were screened at regional cancer centers or affiliated centers that offered CBE had a higher false-positive rate than women screened at affiliated centers that offered only mammography (initial screen: 12.5% and 12.4%, respectively, vs 7.4%; subsequent screen: 6.3% and 8.3%, respectively, vs 5.4%).


CONCLUSIONS
Women should be informed of the benefits and risks of having a CBE in addition to mammography for breast screening.