Genetic testing for cancer susceptibility saves lives as well as costs for the healthcare system. Patients with genetic predispositions to cancer may benefit from earlier and more frequent monitoring and/or preventative treatments. Multiple genetic variants explain up to 50% of breast cancers in particular, the mutations in the BRCA1 and BRCA2 genes for explain about 10% of breast and ovarian cancers. So why is it so difficult to get access to a genetic test for breast cancer susceptibility? In Ontario, according to the Ministry of Health and Long Term Care guidelines, only certain individuals with a risk of having a mutation in these genes, based largely on family history, qualify for testing.
Breast cancer affects over 23,800 women in Canada every year and accounts for 30% of all cancers. The incidence of breast cancer has almost tripled in the past four decades partly due to the increased life expectancy of Canadians, but, even accounting for the increased life span, the incidence of breast cancer has increased by more than 50%. New therapies and increased screening for breast cancer have halted the rise in mortality, with survival rates improving substantially over the years.
Genetic testing for breast cancer susceptibility (BRCA1 and BRCA2) has saved lives by ensuring that at-risk individuals can have preventative treatment and monitoring to detect tumors at a much earlier stage. In Canada, mammography is now recommended for women over the age of 50, while women with BRCA1 or BRCA2 mutations develop tumors at a much earlier age. Therefore, a many women with BRCA mutations will develop cancer even before their first mammography examination if their carrier status is unknown. Consequently, the province of Ontario has expanded the Ontario Breast Cancer Screening program for women at high risk to cover the age group 30-69 years. But is examination of the family history of cancer is accurate enough?
Although women with a family history of breast cancer are at higher risk, a family history of breast cancer is not predictive of the age of onset in population screening scenario because the BRCA mutations still account for 10-15% of attributable risk for breast cancer, and ~30% of ovarian cancers. The guidelines assumes that family history is a good predictor for risk, but what happens if the BRCA1 or BRCA2 mutation came from the paternal side of the family?
Males with BRCA mutations have a 5% lifetime risk of developing breast cancer or melanoma, but for women carrying BRCA mutations the lifetime risk is much higher: over 80% for breast cancer and 50% for ovarian cancers. Variable penetrance of BRCA mutations poses a challenge for accurate assessment of family history of cancer. The mutation can pass through paternal lines for generations largely unnoticed, particularly if the family history is incomplete or is masked by other fatal diseases, giving a false sense of security to physicians and women. The probability of cancer manifestation is greater in larger families, thus women from smaller families are at a “disadvantage”.
Currently, according to the Ministry’s guidelines the family history of cancer in men is dismissed as irrelevant for their daughters when the Ministry of Health is determining the eligibility for BRCA testing, but in reality, these women are at higher risk than families with no history of cancer. Therefore, some of the women in need for BRCA testing will not get tested or get reimbursed if they elect to get screened.
Secondly, Ontario has recognized the increased risk of heritable cancers in the Ashkenazi Jewish population, but with extensive intermarriage in European and North American populations, some people find that they carry “Ashkenazi” mutations but do not consider themselves as Jewish – a good example is the actress Angelina Jolie who was screened because of strong family history of cancer.
Furthermore, genetic research for heritability of breast cancer has identified over 76 genes are responsible for breast cancer risk and when taken together can account for 50% of disease heritability. In addition to BRCA1 and BRCA2 genes, mutations in the ATM, p53, CHEK2, PTEN, BRIP1, XRCC2, PALB2, LKB1 genes are also linked to breast (and other types of) cancer. Thus, limiting the test to two genes to estimate disease risk for breast cancer is not very meaningful.
Now, new technologies allow cost-effective sequencing of the genome to identify predispositions to cancer, cardiovascular, neurodegenerative and autoimmune diseases, all of which can benefit from personalized disease prevention and screening approaches. Such testing would need to be conducted only once in a lifetime but the genetic information obtained would provide insights for health improvement throughout an individual’s life span. The sooner people learn about their inherited risks the more time they will have to act and change their fate.
To learn more about how to get genetic testing for breast cancer, check out our blog on “Where to get Genetic Testing for Breast Cancer in Canada?”. If you have further questions, please also feel free to call or email us.
55 Avenue Road, East Tower, Suite 2000
Toronto M5R 3L2
Telephone 416-849-5555 or email firstname.lastname@example.org
Individualized breast screening/imaging recommendations
Risk reduction strategies
Family history assessment to determine likelihood of eligibility for OHIP coverage of BRCA testing
Arrange for BRCA1 & 2 and possibly ‘panel’ testing for those not eligible for OHIP funded BRCA testing
Facilitate referral for those who are eligible to Ontario High Risk Breast Screening Programs or Familial Breast Cancer Clinics.