Cancer screening

CITES ONLY THESE RESULTS SAYING THAT AT LEAST 1 IN 3 ARE OVERDIAGNOSED Method 1: tries to account for the relatively lower incidence of advanced cancers in the screening areas and includes older women • 9.9% invasive • 16.4% invasive plus DCIS Method 2: does not account for the relatively lower incidence of advanced cancers in the screening areas • 38% invasive • 48% invasive plus DCIS Both methods: overdiagnosis is expressed relative to cases that would be detected without screening, not as a fraction of screen-detected cases “The numbers match those found in other studies that cast doubt on whether mammograms actually reduce the risk of dying from breast cancer. A 2012 study published in the New England Journal of Medicine that found that as many as a third of cancers detected through routine mammograms may not be life threatening.” “It’s simply not valid to cherry-pick findings of nonrandomized studies to support one’s views.” What about clinical trials of screening? Screening trials should be ideal for estimating overdiagnosis • Concurrent control group Most screening trials do not generally produce unbiased estimates • Depends on design (stop-screen or continuous-screen) • Depends on measure used (cumulative or annual incidence) • Depends on timing of the estimation procedure – need to wait