Study design of randomized controlled clinical trials of breast cancer screening

Screening Mammography Among Older Women: A Review of United States Guidelines and Potential Harms

In the United States, older women (aged ≥65 years) continue to receive routine screening mammography surveillance, despite limited evidence supporting the benefits to this subpopulation. This article reviews screening mammography guidelines and the potential harms of such screening for older women in the United States. Published guidelines and recommendations on screening mammography for older women from professional medical societies and organizations in the United States were reviewed from the mid-20th century to present. Observational data were then synthesized to present the documented harms from screening mammography among older women. In 1976, the American Cancer Society recommended to screen all women aged ≥40 years with no upper age limit. With time, other major U.S. medical societies adopted their own screening guidelines without a consensus on age of screening cessation. A population-wide screening effort has largely continued without an upper age limit and with it, a growing body of literature on the harms of screening older women. Reported harms from screening mammography procedures have included physical pain, psychological distress, excessive use of health services from overdiagnoses/false positives, and undue financial expenses. These costs are particularly pronounced among special populations with limited life expectancies such as those of very advanced age ≥80 years, long-term nursing home residents, and the cognitively impaired. When potential harms, remaining life years, and the viability of available treatments are considered, the burdens of screening mammography often outweigh the benefits for older women. For some cases, an individualized approach to recommendations would be appropriate. National guidelines should be updated to provide clear guidance for screening women of advanced age, especially those in special populations with limited life expectancies.

Screening for bladder cancer: theoretical and practical issues in considering the treated and untreated natural history of the various forms of the disease

Screening is used to detect disease earlier in its course, allow earlier treatment, and presumably decrease morbidities and potential mortality associated with the later expression of more advanced disease and presumably more complex treatments consequently required. Judicious screening in bladder cancer depends on an understanding of how the different forms of bladder cancer express their biological potential, whether the tools available for screening have sufficient sensitivity and specificity to have accurate predictive value in accurately diagnosing and assessing each cancer diathesis earlier in its course, and how this may influence the morbidities and mortality associated with each. The principles of screening, potential biases that can affect their accuracy and the interpretation of outcomes, tools currently available for screening, their efficacies and pitfalls, and lessons learned from studies of the role of screening in prostate cancer will be reviewed to offer an understanding of the potential role that screening may play in the different forms of bladder cancer in the context of their preclinical and treated natural history.

Design and analysis of controlled trials in naturally clustered environments: implications for medical informatics

In medical informatics research, study questions frequently involve individuals who are grouped into clusters. For example, an intervention may be aimed at a clinician (who treats a cluster of patients) with the intention of improving the health of individual patients. Correlation among individuals within a cluster can lead to incorrect estimates of the sample size required to detect an effect and inappropriate estimates of the confidence intervals and the statistical significance of the intervention effects. Contamination, which is the spread of the effect of an intervention or control treatment to the opposite group, often occurs between individuals within clusters. It leads to an attenuation of the effect of the intervention and reduced power to detect a difference. If individuals are randomized in a clinical trial (individual-randomized trial), then correlation must be taken into account in the analysis, and the sample size may need to be increased to compensate for contamination. Randomizing clusters rather than individuals (cluster-randomized trials) can eliminate contamination and may be preferred for logistical reasons. Cluster-randomized trials are generally less efficient than individual-randomized trials, so the tradeoffs must be assessed. Correlation must be taken into account in the analysis and in the sample-size calculations for cluster-randomized trials.

Breast cancer screening

Breast cancer is the most common malignancy among women in the United States; however, recent data demonstrates a decline in the mortality rate, which may be attributed to early detection from screening programs combined with effective therapies for early stage disease. As a result of the prevalence of breast cancer and its association with highly emotional issues, screening recommendations have aroused debate in the scientific, public, and legislative domains. A general consensus supports breast cancer screening among women between the ages of 50 and 70; however, much controversy exists regarding screening for women age 40 to 49 or above age 70. This article explores the issues involved in determining breast cancer screening recommendations among asymptomatic women with average risk in the United States.

Breast cancer screening

Randomized controlled trials involving nearly 500,000 women on two continents have confirmed the early promise that screening mammography can reduce breast cancer mortality. The observed benefits of mammographic screening, however, are not the same in all women. The mortality reduction in women over age 70 is unknown, and women aged 40 to 49 do not appear to benefit from mammographic screening to the same extent as those over age 50. The reasons for this disparity are incompletely understood, but it depends in part upon differing tumor biology and mammographic test characteristics in younger women. Even if relative survival benefits were equal for women under and over age 50, absolute reduction in risk would remain considerably lower for younger women, a disparity that would not be corrected by improved screening technology or adjustment of interscreening intervals. The authors' review of the evidence leads them to strongly support mammographic screening of women aged 50 to 69 at an interval not longer than 2 years. The authors also feel it is reasonable to screen women over age 70 who have a favorable life expectancy. They conclude, however, that the evidence does not support a blanket recommendation in favor of screening women aged 40 to 49. Instead, they advocate a well-informed conversation between physician and patient regarding the present knowledge and the risks and benefits of screening for each individual woman. Definitive answers await the results of ongoing RCTs designed to study the survival benefit conferred by screening women aged 40 to 49. Disagreement will undoubtedly persist regarding which recommendations should determine private practice and public policy.