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

Lead Contacts and/or Principal Investigators (PIs):

Funded Since: 1998
Funding Source: NCI Extramural Program (Epidemiology and Genomics Research Program, Division of Cancer Control and Population Sciences; CA077398External Web Site Policy)
Year(s) of Enrollment: 1995-1996
Study Website: http://www.calteachersstudy.org/index.htmlExternal Web Site Policy

A cohort of 133,479 California public school teachers, administrators, and other school professionals was established by a collaborative group of epidemiological investigators at the City of Hope, University of Southern California, University of California at Irvine, and Cancer Prevention Institute of California. The goals of the California Teachers Study (CTS) were, and continue to be, to evaluate unresolved issues related to breast and other cancer risk factors, and study other important issues related to women's health.

The participants were recruited through the California State Teachers Retirement System and completed a detailed multiple-choice, optically scanned mail survey in 1995-1996. Three subsequent questionnaires have been completed by study participants. Follow-up of the cohort includes routine linkage with the California Cancer Registry, which is more than 99 percent complete and therefore identifies all participants in California (>91% of the cohort) who are diagnosed with cancer. The cohort is also linked with the State of California hospital discharge database, on an annual basis which provides information on all discharge diagnoses and procedures that are performed on participants living in the state. For mortality follow-up, the cohort is linked with California mortality files, the Social Security Death Index, and the National Death Index, providing mortality data for the entire cohort including cause of death. As of December 31, 2007, 116,677 cohort members remain alive and are in active follow-up. Annual recontact of cohort members for follow-up is completed through the mailing of an annual newsletter to members, of whom 88% of them are currently alive and reside in California.

The aims are to test a series of unresolved and emerging hypotheses related to breast cancer etiology as well as the etiology of other cancers and common conditions among women including fibroids, endometriosis, diabetes, and asthma.

Numbers of incident invasive cancers (for selected diagnoses) occurring among cohort participants living in California through December 31, 2007, are shown in the accompanying table:

The CTS 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. More than 80 papers have been published from the CTSExternal Web Site Policy.

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