To the Editor In their Viewpoint, Adami et al¹ indicated that early detection screening tests 鈥渨ork by detecting cancer early and thus reducing death from cancer.鈥� However, it is also important to acknowledge that there is a strong treatment interaction associated with cancer screening.² Thus, as cancer treatments improve over time, the mortality benefit of screening will diminish. This is particularly evident in the historical overview of the 9 successive mammography screening trials.² The oldest of those trials was initiated in 1963, before effective adjuvant systemic therapies were available. Using a large sample of women enrolled in the Health Insurance Plan of Greater New York, the trial demonstrated that mammography screening reduced the risk of breast cancer deaths by nearly 30%. Subsequent mammography screening trials showed diminishing mortality benefit attributable to screening, with the 3 most recent trials, the Canadian National Breast Screening Study (CNBSS) I and II, and the UK Age Trial, showing no benefit at all. Effective adjuvant systemic therapies were widely available to patients enrolled in the CNBSS I, CNBSS II, and UK Age Trial, but not the earlier trials.