Elsevier

Annals of Epidemiology

Volume 12, Issue 1, January 2002, Pages 27-33
Annals of Epidemiology

Original reports
Characteristics Associated with Participation at Various Stages at the Ontario Site of the Cooperative Family Registry for Breast Cancer Studies

https://doi.org/10.1016/S1047-2797(01)00253-8Get rights and content

Abstract

PURPOSE: The Ontario site of the Cooperative Family Registry for Breast Cancer Studies collects cancer family history, other risk factor information, and biospecimens from individuals with incident breast cancer and their relatives within a defined population. Sampling is based on age and defined genetic risk criteria. The purpose of this analysis was to evaluate the representativeness of the respondents.

METHODS: We examined characteristics associated with response to requests for information, biospecimens, and permission to contact relatives among those diagnosed with breast cancer in 1996 in the province of Ontario.

RESULTS: Overall, response was good among the largest group, white women, and did not differ between those with and without a family history of breast and/or ovarian cancer. Women who described themselves as other than white and men tended to have lower response. Women of Ashkenazi heritage had high response except for permission to contact relatives.

CONCLUSIONS: There was no evidence that participation in a familial breast cancer registry derived from a population-based cancer registry was influenced by having a family history of breast or ovarian cancer. The use of a cancer registry approach is likely more representative of the population than clinic-based recruitment of families for genetic studies.

Introduction

It is known that genetics plays a role in the development of at least some breast cancers. One of the most consistently identified risk factors in this disease is having a first degree relative with breast cancer. This approximately doubles the risk (1). Mutations in the BRCA1 and BRCA2 genes are associated with a greater increase in risk in the small number of individuals who carry them, although estimates of risk vary 2, 3, 4. Other genetic alterations and variations have also been implicated with varying degrees of consistency in breast cancer development 5, 6. Many studies of breast cancer genetics, particularly of BRCA1 and BRCA2, have been carried out in families with multiple cases of breast and/or ovarian cancer. Although these families are useful for identifying high-risk mutations, they cannot be used to accurately determine the penetrance of the mutations in the population as any mutations in families with fewer cases and lower penetrance will be excluded.

The U.S. National Institutes of Health has created the Cooperative Family Registry for Breast Cancer Studies (CFRBCS) in order to develop a large resource including family history, epidemiologic, and clinical information as well as biospecimens to study the role of genetics in breast cancer. The CFRBCS consists of six sites, four based in the U.S., one in Australia, and one Ontario, Canada. Three of the U.S. sites accrue participants in the registry through high risk cancer genetics clinics, while the other three registries identify potential participants through population-based cancer registries. One of the goals of these sites is to obtain population-based measures of penetrance and prevalence of known genetic mutations and variations as well as conducting other population-based studies of genetics and breast cancer. Therefore, it is clearly important that the individuals recruited are as representative as possible of a defined population. In an effort to determine the extent of selection occurring in the Ontario registry, we analysed participation in cases diagnosed in 1996. We examined characteristics associated with response at different stages where a choice could be made about participation and where we had information available. This information included age, sex, and, for stages subsequent to the initial family history screening questionnaire, ethnicity, and family history. Of particular concern was whether response differed by the presence of a family history of breast and/or ovarian cancer.

Section snippets

The Ontario Familial Breast Cancer Registry

The Ontario Familial Breast Cancer Registry (OFBCR) uses a staged approach to recruiting participants to the registry, with follow-up occurring at all stages. The first step was the ascertainment of probands through the Ontario Cancer Registry (OCR). The OCR employs a passive voluntary system of registration of all cancers occurring in the over 10 million residents of Ontario. Studies carried out by the OCR estimate a completeness of case ascertainment for female breast cancer of 97.5% (7). For

Probands

We identified 2728 incident cases of invasive breast cancer (ICD9 174 and 175) diagnosed in 1996 with an available pathology report from the OCR. This included 1981 female cases aged 20 to 54 years, 718 female cases aged 55 to 69 years (sampled at 35%), and 29 male cases aged 20 to 79 years. Only 46 cases (1.7%) were excluded because they had died. Of the remaining 2682 cases, 13 were approached directly at cancer genetics clinics and physician contact was made for 2653 (99%) of the remaining

Discussion

Since our intention was to create a population-based registry, it was important to address the potential for bias among participants. Family history did not appear to affect participation, but women whose ethnicity was other than white and also men were less likely to participate than were white women. The results presented here were not altered by multivariate modelling. A particular concern was differential participation based on genetic risk. The agreement rate of physicians was very high

Acknowledgements

This work was supported by The Division of Cancer Epidemiology and Genetics, the National Cancer Institute of Health and Human Services, U01-CA69467, and by Cancer Care Ontario.

References (10)

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