Uptake of clinical genetic testing for ovarian cancer in Ontario: A population-based study
Introduction
Mutations in BRCA1 and BRCA2 account for the majority of cases of hereditary ovarian cancer [1]. Approximately 13% of all invasive ovarian cancers are attributable to a BRCA1 or BRCA2 mutation. The prevalence of BRCA1 and BRCA2 mutations is much higher in Jewish women with ovarian cancer, ranging from 29 to 41% [2], [3]. Previous research has shown that there are several predictors of a BRCA1 or BRCA2 mutation in women with ovarian cancer including age, histology, family history of cancer, and personal history of breast cancer [10].
Genetic testing for BRCA1 and BRCA2 mutations is offered to high-risk women (primarily based on family history of breast and/or ovarian cancer) in the context of the universal healthcare system in Ontario, Canada. Because of the high appreciable prevalence of BRCA1 and BRCA2 mutations in women with ovarian cancer, the Ontario Ministry of Health extended the criteria for genetic testing in 2001 to include all women with a diagnosis of invasive ovarian or fallopian tube cancer. It is not yet known what is the uptake of genetic testing in women diagnosed with invasive ovarian cancer in Ontario after the introduction of this policy.
The process for genetic testing for BRCA1 and BRCA2 begins with a referral from a treating physician to a cancer genetics centre, where genetic counselling is initiated. Individuals who qualify for genetic testing provide blood samples, which are sent for testing to an Ontario Ministry of Health laboratory. In general, patients rely on physician referral for genetic testing. The purpose of this study was to assess to what extent the expanded policy for genetic testing for BRCA1 and BRCA2 in Ontario, Canada is reflected in patient referral patterns. We sought to determine which factors predict the uptake of genetic testing amongst women who are newly diagnosed with ovarian or fallopian tube cancer in Ontario.
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Study population
The study protocol received full ethics approval from the participating institutions. All Ontario patients who had been diagnosed with epithelial ovarian or fallopian tube cancer, from 2002 to 2004, were identified using the Ontario Cancer Registry. For each case, the pathology report was reviewed to determine eligibility and histological type of the tumor. Eligible patients were 20 to 79 years of age and were residents of Ontario at the time of diagnosis. The attending physician of each
BRCA1 and BRCA2 analysis
Lymphocyte DNA was prepared from whole blood. All samples were screened for 11 common mutations (seven in BRCA1 and four in BRCA2), including the three mutations common to Ashkenazi Jews and others of Eastern European ancestry and six mutations previously identified in the French Canadian population [4]. Nine of these mutations were assayed using a rapid multiplex method [5]. We tested separately for the presence of the 6-kilobase (kb) duplication in exon 13 of BRCA1 [6] and for the mutation
Statistical analysis
We determined the number of women who had undergone genetic testing prior to the study. We then compared the proportion of positive genetic tests results between women tested previously and those tested as a component of the research study. We compared the women who had and who had not received prior genetic testing for a number of demographic and other variables, including age, education, area of residence and treating hospital.
Results
Four hundred and sixteen women participated in the study; 397 of the women had ovarian cancer and 19 had fallopian cancer. The mean age of the women at time of cancer diagnosis was 57.5 years (range 23–79) (Table 1). The majority of women were white and had an education beyond high school. Seven percent of the women had a family history of ovarian cancer, 17% had a family history of breast cancer, and 7% had a personal history of breast cancer (mean age of diagnosis 49.2 years). Of the 416
Discussion
Ontario women with invasive ovarian cancer or fallopian tube cancer are now eligible for genetic testing for BRCA1 and BRCA2 mutations under the provincial health care plan. However, only 19% of the eligible women in our study had actually undergone genetic testing prior to study contact.
Risch et al. identified several predictors of a BRCA1 or BRCA2 mutation in women with ovarian cancer including age, histology, family history of cancer, and personal history of breast cancer [10]. Factors which
Conflict of interest statement
The authors declare that there are no conflicts of interest.
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