Analysis of Mortality Data From Cancer Screening Studies
- 1 November 2005
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Epidemiology
- Vol. 16 (6), 786-790
- https://doi.org/10.1097/01.ede.0000181313.61948.76
Abstract
Appropriate statistical analysis is required to measure the impact of early detection and treatment of cancer. The current practice of using cumulative mortality ignores both (1) the delay between early treatment and the time that any averted deaths would have otherwise occurred, and (2) cessation of these delayed benefits some time after screening is discontinued. We use time-specific mortality density ratios to estimate the mortality ratio in the "window of influence." We then use time-specific incidence density ratios to assess the extent to which the removal of polyps and other possibly precancerous lesions detected by fecal occult blood screening reduces the incidence of colorectal cancer. Applied to a theoretical example, the current practice of using cumulative mortality substantially underestimates the reduction in mortality achievable by early treatment. If there is sufficient time for the full impact to emerge, time-specific mortality patterns provide a more accurate measure. In a previous analysis of the screening study, the reduction in cumulative incidence in the screened groups was just under 20%. In our reanalysis, yearly incidence density ratios indicate that had screening not been interrupted, there might have been a 40% reduction in incidence. Time-specific mortality ratios provide a more sensitive measure of the effects of early detection and treatment. Measures based on cumulative mortality are diluted by inclusion of deaths that occur soon after the initiation of screening as well as deaths that occur too long after the cessation of screening.Keywords
This publication has 13 references indexed in Scilit:
- A case-control study to estimate the impact on breast cancer death of the breast screening programme in WalesJournal of Medical Screening, 2004
- Natural experiment examining impact of aggressive screening and treatment on prostate cancer mortality in two fixed cohorts from Seattle area and ConnecticutBMJ, 2002
- Needs Assessment of Women With Urinary Incontinence in a District Health AuthorityJournal of Urology, 2002
- Mammographic screening: no reliable supporting evidence?The Lancet, 2002
- International trends in prostate-cancer mortality in the ?PSA era?International Journal of Cancer, 2001
- The Effect of Fecal Occult-Blood Screening on the Incidence of Colorectal CancerNew England Journal of Medicine, 2000
- Comparison of trends in prostate-cancer mortality in England and Wales and the USAThe Lancet, 2000
- Is screening for breast cancer with mammography justifiable?The Lancet, 2000
- Colorectal Cancer Mortality: Effectiveness of Biennial Screening for Fecal Occult BloodJNCI Journal of the National Cancer Institute, 1999
- Prostate cancer incidence and mortality in the United States and the United Kingdom.JNCI Journal of the National Cancer Institute, 1998