Clinical Breast Exam as an Adjunct to Mammography
Clinical Breast Exam as an Adjunct to Mammography
Abstract & Commentary
By William B. Ershler, MD
Synopsis: The role of clinical breast examination remains controversial. A review of data from the Ontario Breast Cancer Screening Program reveals that cancer detection rates and sensitivity were higher, as were the abnormal call rates and false positive rates among centers that offered CBE in addition to mammography compared to centers that offered mammography alone.
Source: Chiarelli AM, et al. The contribution of clinical breast examination to the accuracy of breast screening. J Natl Cancer Inst. 2009;101:1236-1243.
The data regarding the value of mammography screening in reducing breast cancer mortality has been established by several randomized trials,1 but there remains controversy about whether adding clinical breast examination (CBE) to mammography improves the accuracy of breast screening. To address this, Chiarelli et al from Toronto compared the accuracy of screening among centers that offered CBE in addition to mammography with those that offered only mammography.
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 (OBSP) between January 1, 2002 and December 31, 2003, and were followed up for 12 months. The OBSP included programs at the nine regional cancer centers and 93 affiliated centers. 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 regional cancer centers or at the 59 affiliated centers that provided CBE were compared with those for 57,715 women who were screened by mammography alone at 34 affiliated centers.
Sensitivity of referrals was higher for women who were screened at centers that offered CBE in addition to mammography than for women screened at centers that did not (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 mammography only (initial screen: 12.5% and 12.4%, respectively vs. 7.4%; subsequent screen: 6.3% and 8.3%, respectively vs. 5.4%).
The pattern of an increased sensitivity and false-positive rate in centers that offered CBE compared with centers that did not was also observed after adjusting for characteristics of the women, the facilities, and the providers. Among all centers that offered CBE, the cancer detection rate for mammography referrals was calculated to be 5.9 per 1,000 and for CBE and/or mammography referrals 6.3 per 1,000; the false-positive rate for mammography referrals was 6.5% and for CBE and/or mammography referrals 8.7%. Therefore, with CBE, an additional 0.4 cancers are detected per 1,000 women screened, with an increase of 2.2 percentage points in the false-positive rate. Accordingly, for 10,000 women screened, there would be an additional four cancers detected and, of the 9,937 women without cancer (based on the observed 63 cancers detected per 10,000 women), there would be an additional 219 false-positive screens. Therefore, for each additional cancer detected by CBE per 10,000 women, there would be 55 additional false-positive screens.
Commentary
Overall, this study revealed that cancer detection rates and sensitivity were higher, as were the abnormal call rates and false-positive rates among centers that offered CBE in addition to mammography than among centers that offered only mammography. The benefit in increased sensitivity needs to be balanced against the potential risks and costs of further follow-up due to false-positive results, as well as the anxiety associated with additional diagnostic evaluations. Furthermore, with regard to the generalizability of these findings, it should be recalled that CBE was performed by a specially trained staff of professionals, each of whom performed this prescribed systematic evaluation several thousand times each year. Whether results would be comparable if performed by less well-prepared practitioners would seem unlikely, and this alone might diminish the modest benefit in sensitivity and expand the number of false-positive reports. Furthermore, the analysis included women aged 50-69 years, and clearly results regarding both sensitivity and specificity should not be extrapolated beyond this range.
Thus, even though CBE adds sensitivity to the overall breast-screening program, there remain concerns even when performed under optimal circumstances, such as by the OBSP, regarding the added number of false-positives reports. Certainly, when performed, women should be informed of the benefits and risks of having a CBE as an adjunct to mammography for breast-cancer screening.
References
1. Humphrey LL, et al. Breast cancer screening: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2002;137:347-360.
The role of clinical breast examination remains controversial. A review of data from the Ontario Breast Cancer Screening Program reveals that cancer detection rates and sensitivity were higher, as were the abnormal call rates and false positive rates among centers that offered CBE in addition to mammography compared to centers that offered mammography alone.Subscribe Now for Access
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