The quality and interpretation of mammographic screening trials for women ages 40-49

Using MEDLINE and the bibliographies of retrieved articles and reviews, we identified and systematically reviewed the quality and results of all randomized trials of mammographic screening that included women less than 50 years of age. Eight randomized trials were identified, 7 of which included women less than 50. Identified trials were assessed for the following design features: (a) method of randomization, (b) documented comparability of baseline data, (c) standardized criteria for breast cancer death, (d) blinded review of cause of death, (e) completeness of follow-up, and (f) use of an "intention to treat analysis." The quality of trials was generally high, with a total of almost 160,000 women randomized. In women aged 40-49 at entry, the overall, absolute risk difference between those invited and those not was 0.0004 (95% CI: 0 to 0.0009). Yet, what does this mean to a 40-year-old women considering screening? If 10,000 women aged 40-49 years were screened regularly, then after a decade there would be about 4 less breast cancer deaths? Is that worthwhile? This is a difficult question, and it needs to be weighed against the problems arising from false positives and ductal carcinoma in situ. We recommend that women in this age group intending to be screened should be fully informed of these results in terms of absolute benefit.