Estimates of the number of US women who could benefit from tamoxifen for breast cancer chemoprevention.
BACKGROUND
The Breast Cancer Prevention Trial demonstrated that tamoxifen treatment produced a 49% reduction in the risk of invasive breast cancer among women at elevated risk for the disease. The U.S. Food and Drug Administration (FDA) subsequently approved tamoxifen for women aged 35 years or older with a 5-year breast cancer risk of 1.67% or higher for breast cancer chemoprevention. However, tamoxifen use has been associated with adverse outcomes, and not all eligible women have a positive benefit/risk ratio.


METHODS
We used weighted data from the year 2000 National Health Interview Survey Cancer Control Module to estimate the total number of U.S. women, aged 35-79 years, who were eligible for tamoxifen chemoprevention based on the FDA eligibility criteria. We also estimated the numbers of white and black women who would benefit from tamoxifen chemoprevention on the basis of a positive benefit/risk index developed by Gail et al.


RESULTS
Of the 65,826,074 women aged 35-79 years without reported breast cancer in the United States in 2000, 10,232 816 women (15.5%, 95% confidence interval [CI] = 14.7% to 16.3%) would be eligible for tamoxifen chemoprevention. The percentage of U.S. women who would be eligible varied dramatically by race, with 18.7% (95% CI = 17.8% to 19.7%) of white women, 5.7% (95% CI = 4.3% to 7.5%) of black women, and 2.9% (95% CI = 2.1% to 3.9%) of Hispanic women being eligible. Of the 50,104,829 white U.S. women aged 35-79 years, 2,431,911 (4.9%, 95% CI = 4.3% to 5.4%) would have a positive benefit/risk index for tamoxifen chemoprevention. Of the 7,481,779 black U.S. women aged 35-79 years, only 42,768 (0.6%, 95% CI = 0.2% to 1.3%) would have a positive benefit/risk index. Among white women, 28,492 (95% CI = 24,693 to 32,292) breast cancers would be prevented or deferred if those women who have a positive net benefit index took tamoxifen over the next 5 years.


CONCLUSIONS
A substantial percentage of U.S. women would be eligible for tamoxifen chemoprevention according to FDA criteria, but a much smaller percentage would have an estimated net benefit. Nevertheless, this latter percentage corresponds to more than two million women.
Freedman
Andrew N
AN
Division of Cancer Control and Population Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-7344, USA. Andrew_Freedman@nih.gov
Graubard
Barry I
BI
Rao
Sowmya R
SR
McCaskill-Stevens
Worta
W
Ballard-Barbash
Rachel
R
Gail
Mitchell H
MH
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000367:Age Factors; D000368:Aged; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D004608:Eligibility Determination / Q000706:statistics & numerical data; D005260:Female; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D008875:Middle Aged; D018570:Risk Assessment; D012307:Risk Factors; D020845:Selective Estrogen Receptor Modulators / Q000627:therapeutic use*; D011795:Surveys and Questionnaires; D013629:Tamoxifen / Q000627:therapeutic use*; D014481:United States / Q000453:epidemiology; D014486:United States Food and Drug Administration; D044465:White People / Q000706:statistics & numerical data
D016588:Anticarcinogenic Agents; D018931:Antineoplastic Agents, Hormonal; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen