1. Optimal screening recommendation: Biennial mammography from ages 40-74 provides the best balance between mortality reduction and screening harms for average-risk women.
2. Starting earlier matters: Beginning screening at age 40 versus age 50 prevents up to 19% more breast cancer deaths with only modest increases in false positives and overdiagnosis.
3. Annual vs. biennial trade-offs: Annual screening prevents only two additional deaths per 1,000 women but substantially increases harms including hundreds more false positives and additional overdiagnosed cases.
4. Shared decision-making is essential: The USPSTF emphasizes that physicians and patients should discuss individual risks and preferences when selecting a screening approach.
5. Foundation based on historical trials: Evidence from randomized controlled trials from the 1960s-1990s showed 14-32% mortality reduction, though current screening and treatment differ from these historical studies.

Source: Annals of Internal Medicine