Evidence to Support Screening Women in Their 40s.

A large body of evidence demonstrates a 30% to 50% mortality benefit of screening mammography for women aged 40 to 49. Because of more rapid cancer growth rates in younger women, annual screening is more effective than biennial. Studies indicate that selective screening of women aged 40 to 49 would miss the majority of breast cancers. If implemented, recent US Preventive Services Task Force breast cancer screening guidelines, which recommend against routine screening of women in their 40s, could result in thousands of preventable breast cancer deaths per year. Vigilance is needed to safeguard younger women's access to screening mammography.