RSS Feeds
Screening Mammography for Younger Women: Back to Basics
- Harold Sox, MD, Editor
This issue of Annals adds fuel to the breast cancer screening debate. It contains the U.S. Preventive Services Task Force's recommendations on breast cancer screening, a summary of the supporting evidence, an editorial about dealing responsibly with conflicting evidence, and a report from the Canadian National Breast Screening Study (CNBSS). The CNBSS randomly assigned 50 304 women age 40 to 49 years to receive mammography and breast examinations five times annually or to receive usual care. The article in this issue by Miller and colleagues (1), the third report from this trial, uses data on breast cancer mortality 11 to 16 years after the first screening visit to address the question, “Is a woman less likely to die of breast cancer if she starts screening while she is in her forties?”
Despite a large study population, careful study design and execution, and long follow-up, the Canadian study still doesn't tell us for certain whether screening helped, harmed, or had no effect. The point estimate of the cumulative rate ratio for death from all breast cancer among screened women is 0.97, indicating no effect of screening. The 95% confidence interval (CI) around this ratio sets limits on the potential benefit and harm. The lower bound (0.74) means that screening is unlikely to reduce breast cancer mortality by more than 26%, or one death per 10 000 women per year. The upper bound (1.27) means that screening is unlikely to increase breast cancer deaths by more than one death per 10 000 women per year.
I suggest four options for dealing with the CNBSS in the light of all available evidence about breast cancer screening …
