Breast cancer screening among women younger than age 50: a current assessment of the issues.

In the hope of resolving underlying policy questions related to the value of breast cancer screening with mammography for women younger than 50 years of age, the National Institutes of Health and the National Cancer Institute in 1997 jointly sponsored a consensus conference on the subject. While the panel concluded that the data were insufficient to endorse mammography for this age group apart from individual choice, the conclusion was not the "consensus" sought by many of those with strong opinions on both sides of this issue, and the debate raged on. Prior to the 1997 conference, and since, meta-analyses of trial data and assessments of service screening programs have indicated that breast cancer screening with mammography for women between 40 and 49 meets recommended levels of performance compared with performance in women 50 years and older, especially if programs achieve high quality and screen at 12-to-18 month intervals. Because the detectable preclinical phase is shorter in younger women who develop breast cancer compared with that in women 50 years of age or older, a key component of any screening program for those younger than 50 is an appropriate screening interval. Many of the screening programs that had historically been developed for women in their forties--and whose disappointing results contributed to the confusion and controversy about the efficacy of mammography in younger women--had a 24-month screening interval, which was not found to be of significant benefit for early detection of breast cancer in this age group. While a new emphasis of this controversy has focused on the balance of benefits and harms in women ages 40 to 49, women of all ages need to be fully informed about the benefits and limitations of breast cancer screening--more specifically, what to expect at the time of screening, and what to expect from screening. There are differences in the performance and effectiveness of mammography in different age groups of women aged 40 and older, but these differences are not so great to question the value of screening in any one group. While some questions remain unresolved, the efficacy of mammography in women ages 40 to 49 should no longer be considered controversial.