California Teachers Study: Breast and Other Cancers in the California Teachers' Cohort

Leslie Bernstein, Ph.D.
University of Southern California/Norris Comprehensive Cancer Center
Department of Preventive Medicine, Los Angeles, Calif.
Funded since 1998
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A cohort of 133,000 California school teachers has been established by a collaborative group of epidemiological investigators with the goals of evaluating unresolved issues related to breast cancer risk factors, and studying other important issues related to women's health.

The teachers were recruited with a detailed multiple-choice, optically scanned mail survey in 1995-1996. Scanning of the questionnaires has been completed and data editing is ongoing. Follow-up includes routine linkage with the California Cancer Registry and California mortality files, annual recontact of cohort members for follow-up, and biennial contact for collecting additional risk factor exposure data and information on other health outcomes.

The aims are to:

• test a series of unresolved and emerging hypotheses related to breast cancer etiology (specifically associations with lactation, hormone replacement therapy, abortion/miscarriage, dietary phytoestrogens, fiber, micronutrient consumption, alcohol intake, physical exercise activities, family history of breast and other cancers, and active and passive cigarette smoke exposure);
• conduct calibration/validation studies of the food-frequency questionnaire and self-reported information on family history of breast and other cancers reported in the baseline questionnaire; and
• follow this cohort for this grant period, during which time two or more questionnaires will be mailed to update initial exposure assessments, collect new exposure information, and assess additional disease outcomes for testing novel hypotheses of major importance to women's health in a timely manner.

By 2008, 2,025 invasive incident and 390 in situ incident breast cancers are anticipated, which will provide ample statistical power to address in detail each of the proposed hypotheses.

The California Teachers Study presents a rare opportunity to study women's health because of the size of the cohort, the uniformly high level of education among teachers, their experience with survey instruments, their diversity of exposures and geographic residences, and the relative ease with which they can be followed in California. This research is intended to substantially increase knowledge of preventable risk factors for cancer and other health outcomes.