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Recognizing BRCA gene mutation risk subsequent to breast cancer diagnosis in southwestern Ontario
Canadian Family Physician (2012)
  • Meredith G Vanstone, McMaster University
  • Winsion Chow, Western University
  • Laura Lester, Western University
  • Peter Ainsworth, Western University
  • Jeff Nisker, Western University
  • Muriel Brackstone, Western University
Abstract

Objective To describe the population of women in southwestern Ontario who were diagnosed with potentially preventable BRCA mutation–related breast cancer.

Design Retrospective chart review.

Setting The Cancer Genetics Clinic of the London Regional Cancer Program in London, Ont.

Participants Patients younger than 52 years of age who were referred to the London Regional Cancer Program Cancer Genetics Clinic between 1997 and 2007 for BRCA testing after being diagnosed with breast cancer (N = 1017).

Main outcome measures The proportion of women with BRCA1 or BRCA2 gene mutations and the proportion of women who would have qualified, based on family cancer history, for referral for genetic counseling and testing before their breast cancer diagnoses.

Results Among the 1017 women referred for BRCA testing, 63 women younger than 52 years of age who had been diagnosed with breast cancer were found, subsequent to this diagnosis, to have BRCA1 or BRCA2 gene mutations. Of these, 41 (65%) had family cancer histories that would have qualified them for genetic counseling and testing, according to provincial criteria, before their own breast cancer diagnoses. Of the 63 women, most (81%) had been referred for BRCA gene mutation testing by their oncologists or surgeons.

Conclusion Our results suggest that the diagnosis of breast cancer could have been anticipated, and perhaps in some cases prevented, in up to two-thirds of high-risk women younger than 52 years of age in southwestern Ontario. If the high-risk status of these women had been recognized, they might have had the opportunity to choose genetic counseling, testing, more effective cancer surveillance, and potentially preventive options. The results of this study call for increased public and care provider awareness about hereditary breast cancer risk to promote women’s ability to choose to access genetic counseling.

Breast cancer is the predominant malignancy among women,1 affecting more than 23 000 Canadian women each year.2 Breast cancer related to BRCA gene mutation is an autosomal dominant inherited disease. The lifetime risk of breast cancer for those carrying BRCA mutation is 45% to 87%,3,4 although this appears to be increasing over time,5,6 suggesting a substantial environmental component in the presentation of the abnormal phenotype. The prevalence of BRCA mutations in the general population is not known,7 but risk models hypothesize that 1 in 300 to 1 in 500 unaffected (non-Jewish) women might carry BRCA1 or BRCA2 mutations.8–10 Hereditary breast cancer is thought to account for 5% to 10% of all cancer cases,11 although known mutations such as BRCA and other less common mutations12,13 are estimated to account for only 25% of hereditary breast cancer.14

If a woman is identified as being at high risk of breast or ovarian cancer, she can choose to participate in genetic counseling to discuss surveillance15,16 and prevention strategies.17–24 Magnetic resonance imaging (MRI) has been shown to be 3 times more effective than mammogram for identifying invasive cancers in the breasts of young women.16,25 Bilateral mastectomy and reconstruction, while invasive, provide 85% to 100% protection depending on the procedure.17–19,26 Salpingooophorectomy might reduce the risk of breast cancer by approximately 50%.27 It also might provide about 80% protection from ovarian and fallopian tube cancer.20 Other options include tamoxifen, which affords approximately 50% protection against contralateral breast cancer.22–24

In order to access genetic counseling and BRCA genetic testing in Ontario, women must have an identifiable risk based on personal and family history, as identified through the Ontario Ministry of Health testing criteria.28

The purpose of this study was to identify and describe the population of women in southwestern Ontario who were diagnosed with potentially preventable BRCA mutation–related breast cancer. By recognizing women who were at identifiably high risk before breast cancer diagnosis, but who might not have been offered access to genetic counseling, testing, surveillance, or preventive strategies, we can explore the obstacles to this identification and work to ameliorate this issue.

Keywords
  • informed decision-making,
  • breast cancer,
  • BRCA,
  • genetic counselling
Disciplines
Publication Date
Spring May, 2012
Citation Information
Meredith G Vanstone, Winsion Chow, Laura Lester, Peter Ainsworth, et al.. "Recognizing BRCA gene mutation risk subsequent to breast cancer diagnosis in southwestern Ontario" Canadian Family Physician Vol. 58 (2012)
Available at: http://works.bepress.com/meredith_vanstone/7/