From the Guidelines
The Number Needed to Treat (NNT) for breast cancer screening using clinical breast exams is not recommended due to lack of evidence of mortality benefit, as stated by the American College of Physicians guidance statement 1. This means that there is no established NNT for clinical breast exams as a standalone screening method, and their use is not recommended for average-risk women. Instead, mammography is the preferred screening method, with an NNT of approximately 1,000-1,500 to prevent one breast cancer death over a 10-year period. The American College of Physicians guidance statement 1 emphasizes that clinical breast exams can result in harms, including overdiagnosis and false-positive results leading to overtreatment, and that no guideline recommends screening with clinical breast exams if mammography is available. Some key points to consider include:
- Clinical breast exams are less effective as a standalone screening method compared to mammography
- The American College of Physicians guidance statement recommends against using clinical breast exams to screen for breast cancer in average-risk women of all ages 1
- Mammography is the preferred screening method, with a recommended starting age of 40 years for average-risk women 1
- The decision to discontinue screening mammography should be based on a shared decision-making process informed by the woman's health status and longevity, rather than age alone 1
From the Research
Number Needed to Treat (NNT) for Breast Cancer Screening
- The provided studies do not directly report the Number Needed to Treat (NNT) for breast cancer screening using clinical breast exams.
- However, the studies compare the sensitivity and specificity of different screening modalities, including clinical breast examination (CBE), mammography, ultrasound, and magnetic resonance imaging (MRI) 2, 3, 4.
- The sensitivity of CBE is reported to be 9.1% in one study, which is lower than the sensitivity of MRI (77%), mammography (36%), and ultrasound (33%) 2.
- Another study found that the addition of MRI to mammography increased the combined sensitivity to 94%, while the sensitivity of mammography alone was 39% 3.
- There is no direct evidence to calculate the NNT for breast cancer screening using clinical breast exams, as the studies focus on the sensitivity and specificity of different screening modalities rather than the treatment outcomes 5, 6.
Screening Strategies for Breast Cancer
- Annual screening strategies, including mammography and MRI, are recommended for breast cancer-susceptibility gene (BRCA) mutation carriers 6.
- The American College of Radiology (ACR) and the Society of Breast Imaging recommend annual mammography screening starting at age 40, which provides the greatest mortality reduction, diagnosis at an earlier stage, better surgical options, and more effective chemotherapy 5.
- However, the optimal screening strategy for individual women should consider the benefits and risks of screening, as well as personal acceptance of false-positive results 6.