Hereditary breast and ovarian cancer (HBOC) is an inherited tendency to breast, ovarian and some other cancers, most often caused by a harmful change in the BRCA1 or BRCA2 gene (and sometimes related genes such as PALB2). These genes normally help repair DNA, so a faulty copy allows cancers to arise earlier and more often than average. Crucially, a positive result raises risk but is not a diagnosis — many carriers never develop cancer — and men can carry and be affected too. Every management decision is made with a specialist and genetic counsellor.
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A positive BRCA result means increased risk, not certainty. Management — screening, risk-reducing medication or surgery — is individualised with a specialist. Because the gene change is inherited, a result has implications for your blood relatives.
What it is
HBOC is an inherited predisposition to certain cancers, usually from a pathogenic variant in BRCA1 or BRCA2. These are tumour-suppressor genes that help fix damaged DNA, and a faulty copy weakens that repair. Inheritance is autosomal dominant, so a child of a carrier has about a 1-in-2 chance of inheriting the variant, which is present in every cell. Other genes such as PALB2, CHEK2, ATM and TP53 can also raise risk and may appear on the same test panel.
Family-history red flags
Discuss referral with a doctor if there is a known BRCA or related variant in the family; breast cancer at a young age (around 50 or younger); ovarian, fallopian tube or primary peritoneal cancer at any age; multiple relatives on the same side with breast or ovarian cancer; more than one primary cancer in a relative; breast cancer in a man; a family cluster including pancreatic or high-risk prostate cancer; or certain ancestries with higher carrier frequency, such as Ashkenazi Jewish heritage. Triple-negative breast cancer is more often BRCA1-associated.
What a positive result means
A positive result means an inherited harmful variant that raises the risk of certain cancers — it cannot say whether or when cancer will occur. To give a sense of scale, the US National Cancer Institute estimates that more than 60% of women who inherit a harmful BRCA1 or BRCA2 change may develop breast cancer in their lifetime, compared with about 13% of women in the general population, with ovarian-cancer risk also well above average; these are attributed estimates that vary widely by gene, specific variant and population, not a personal figure. A “variant of uncertain significance” is not an actionable positive and is often later reclassified.
How risk is managed
Options are individualised with a specialist. Enhanced surveillance means starting breast screening younger and adding breast MRI to mammography; importantly, there is no proven effective screening test for ovarian cancer, which is an important expectation to set. Risk-reducing medication (chemoprevention) may be discussed, and risk-reducing surgery — such as mastectomy, or removal of the ovaries and tubes — substantially lowers but does not entirely eliminate risk, and removing the ovaries causes early menopause. These are deeply personal decisions, and this guide gives no medication doses.
Testing and counselling
Testing is preceded and followed by genetic counselling, and usually uses a blood or saliva sample. Where possible it starts with a relative who has or had cancer, to find the family’s specific variant, which makes relatives’ results clearer. Cross-referencing our breast cancer screening guide can help you understand the surveillance side. It is worth knowing that testing negative for a variant already identified in your family (a “true negative”) is genuinely reassuring, whereas testing when no family variant is known gives a less definitive answer, which is one reason counsellors prefer to begin with an affected relative wherever possible.
Family implications and cascade testing
Because the variant is inherited, results have direct meaning for blood relatives. Once a family variant is known, cascade (predictive) testing lets relatives learn their status, and it is recommended for both male and female relatives. A “true negative” — not carrying a known family variant — is reassuring, whereas a negative result with no known family variant is less definitive. Testing of children is generally not recommended where there is no childhood intervention.
Men can carry too
BRCA passes through fathers as well as mothers. Men can develop male breast cancer, have an increased risk of prostate and pancreatic cancer, and can pass the variant to their children, so male relatives should be included in family testing and offered appropriate awareness and screening. This is a commonly missed point that matters for whole-family planning, and it means a BRCA result on either side of the family — the father’s as much as the mother’s — is relevant to sons and daughters alike.
How to access it in Singapore
Assessment is through a hospital cancer genetics service. In Singapore this includes the National Cancer Centre Singapore (NCCS) Cancer Genetics Service, which uses a counsellor-led model and accepts self-referral on 6436 8088 or referral through a GP, as well as NUH and the National University Cancer Institute, KKH and other SingHealth centres. General information is available via HealthHub and the Singapore Cancer Society, and a genetic counsellor will talk through the benefits, limits, costs and emotional side before any test is done.
Related genetics & genomic-health topics
- Genetic testing
- Genetic counselling
- Carrier screening
- Lynch syndrome
- Down syndrome
- Prenatal genetic testing
- Familial hypercholesterolaemia
- Rare & inherited diseases
- Pharmacogenomics
- Thalassaemia
- Paediatricians in Singapore
Sources
- National Cancer Institute — BRCA Gene Changes: cancer.gov
- MedlinePlus — BRCA1 gene: medlineplus.gov
- National Cancer Centre Singapore — Cancer Genetics Service: nccs.com.sg