Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Breast Cancer Health Center

Font Size

Breast Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - Appendix of Randomized Controlled Trials

Health Insurance Plan, United States 1963 [1,2]

Age at entry: 40 to 64 years.
Randomization: Individual, but with significant imbalances in the distribution of women between assigned arms, as evidenced by menopausal status (P < .0001) and education (P = .05).
Sample size: 30,000 to 31,092 in study group and 30,565 to 30,765 in control group.
Consistency of reports: Variation in sample size reports.
Intervention: Annual two-view mammography (MMG) and CBE for 3 years.
Control: Usual care.
Compliance: Nonattenders to first screening (35% of the screened population) were not reinvited.
Contamination: Screening MMG was not available outside the trial, but frequency of CBE performance among control women is unknown.
Cause of death attribution: Women who died of breast cancer that had been diagnosed before entry into the study were excluded from the comparison between the screening and control groups. However, these exclusions were determined differently within the two groups. Women in the screening group were excluded based on determinations made during the study period at their initial screening visits. These women were dropped from all further consideration in the study. By design, controls did not have regular clinic visits, so the prestudy cancer status of control patients was not determined. When a control patient died and her cause of death was determined to be breast cancer, a retrospective examination was made to determine the date of diagnosis of her disease. If this was prior to the study period then she was excluded from the analysis. This difference in methodology has the potential for a substantial bias in comparing breast cancer mortality between the two groups, and this bias is likely to favor screening.
Analysis: Follow-up.
External audit: No.
Follow-up duration: 18 years.
Relative risk of breast cancer death, screening versus control (95% confidence interval [CI]): 0.71 (0.55-0.93) at 10 years and 0.77 (0.61-0.97) at 15 years.
Comments: The MMGs were of poor quality compared with those of later trials, because of outdated equipment and techniques. One should remember that the intervention consisted of both MMG and CBE. Major concerns about trial performance are the validity of the initial randomization and the differential exclusion of women with a prior history of breast cancer.
1 | 2 | 3 | 4 | 5 | 6
1 | 2 | 3 | 4 | 5 | 6
Next Article:

Today on WebMD

Breast Cancer Overview
From self-exams and biopsies to reconstruction, we’ve got you covered.
Dealing with breast cancer
Get answers to your questions.
woman having mammogram
Experts don’t agree on all fronts, but you can be your own advocate.
woman undergoing breast cancer test
Many women worry. But the truth? Most abnormalities aren’t breast cancer.
Breast Cancer Treatments Improving
Resolved To Quit Smoking
Woman getting mammogram
Screening Tests for Women
ovarian cancer overview slideshow
serious woman
what is your cancer risk
10 Ways to Revitalize Slideshow