Multiethinic Cohort Study


The Multiethnic Cohort (MEC) is a prospective cohort study that was designed to provide prospective data on cancer and other chronic diseases 32. To maximize the diversity of exposures the MEC targeted a range of ethnic groups spanning all socioeconomic levels. The MEC includes 215,251 men and women aged 45-75 at recruitment, primarily from five different racial-ethnic groups (AAs, Japanese Americans, Latinos, Native Hawaiians and Whites in Hawaii and California). The cohort was assembled in 1993-1996 by mailing a self-administered, 26-page questionnaire to persons identified primarily through the driver's license files for the state of Hawaii and the county of Los Angeles in California, supplemented with other sources. The cohort encompasses a broad spectrum of persons from each of the ethnic groups sampled.  The distributions of the cohort across educational levels and marital status are fairly similar to census data, suggesting that findings should be broadly generalizable to these populations.  The baseline questionnaire obtained extensive information on demographics, medical and reproductive histories, medication use (including hormonal replacement therapy), family history of various cancers, physical activity and an extensive quantitative food frequency questionnaire (FFQ). In Year 5 of the follow-up, we sent a short questionnaire that updated information on medical conditions, family history of cancer and other diseases, screening tests for cancer and use of HRT and vitamin supplements. We are currently completing the updating of the dietary and other exposure data by re-administration of the full baseline questionnaire with funding by the parent MEC grant (CA 54281, Kolonel, PI).  Receipt of a completed questionnaire was evidence of a desire to participate in the study and was taken as a formal indication of consent; the study was approved by the Institutional Review Boards of the University of Hawaii and University of Southern California.
Identification of incident cancer cases in the MEC is by regular linkage with the Hawaii Tumor Registry (HTR) and the Los Angeles County Cancer Surveillance Program (CSP); both are NCI-funded Surveillance, Epidemiology, and End Results (SEER) registries. The registries ascertain all primary cancer diagnoses among residents of Hawaii and Los Angeles, respectively, and serve as a mechanism for obtaining tumor tissue for population-based research (with an 80% success rate). We also perform an annual linkage with the State of California Cancer Registry, also a SEER registry. From these registries, we obtain the following information about the cancer patients: site, stage, histology, differentiation, grade and disease-specific survival. Deaths in the cohort are identified by linkage to the state death-certificate files in CA and HI, and with the National Death Index for deaths occurring in other states. Out-migration in the MEC is low. Based on the extensive tracking of a random sample of the cohort, we found that the out-migration rate was 3.7% after 7 years of follow-up. Out-migration is expected to decrease over time since, as we previously showed in another cohort in Hawaii, it is highest in the early years of follow-up.

Biospecimen collection in the MEC began in 1996 (CA 054281, Kolonel, PI; CA 63464, Henderson, P.I.) with the collection of blood and urine specimens from incident cases of breast, prostate and colorectal cancer, together with a cross-section of the cohort (N~6,000), for nested case-control studies of genetic susceptibility and cancer.  In the current cycle of P01 CA63619 (Kolonel, PI), and a renewal of CA 63464, the effort was expanded and included the prospective collection of biospecimens (fasting blood, urine, and in a small subset, buccal cells) from all eligible MEC participants in Hawaii and Los Angeles, respectively. At the time of specimen collection, a short questionnaire was administered to update exposures, as well as current medication and dietary supplement use.  This biorepository, completed in 2006, allows us to use a prospective design to examine biomarkers of chronic diseases. Blood and urine samples were collected from 67,594 subjects (31,136 men and 36,458 women), consisting of multiple 0.5 cc aliquots of serum, plasma, buffy coat and washed RBCs stored in vapor phase of liquid nitrogen (LN2) (10-14 straws/subject), and single 1.5 cc aliquots of plasma, buffy coat and clot stored at -80ºC. The subjects signed a consent form at time of blood draw. By the start of year 5, we expect to have a total of 700 cases available for genetic analysis. The collection of FFPE blocks from African American breast cancer case in the MEC has been funded separately (PPG, Univ of Hawaii, PI, L. Kolonel).

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