Hereditary cancer & genetic testing
Five to ten in every hundred cancers are inherited. When it is worth investigating, what genetic counselling involves, and what it means for your family.
The figures at a glance
How many cancers are genuinely inherited
Roughly 5 to 10% of cancers are due to an inherited variant passed from one generation to the next. The great majority of the rest arise from damage accumulating in cells over a lifetime.
The distinction matters, because with hereditary syndromes knowing changes things: it changes how often someone is monitored, sometimes the treatment choice, and it concerns their relatives too.
When suspicion is raised
A family history is worth further assessment when features like these are present:
- Cancer at an unusually young age.
- Several relatives with the same or a related cancer type.
- More than one primary tumour in the same person.
- Particular combinations — breast and ovarian, for instance, or colorectal and endometrial.
- Breast cancer in a man.
BRCA1/2 and Lynch syndrome
The two most common syndromes in practice are BRCA1 and BRCA2 variants — associated mainly with breast and ovarian cancer, but also prostate and pancreatic — and Lynch syndrome, associated with colorectal, endometrial and other cancers.
In both cases identification is not merely information: it leads to specific surveillance programmes and, in some cases, influences treatment choice as well.
What genetic counselling involves
Genetic testing does not begin with a blood sample but with a conversation. The family history is recorded in detail, the value of testing is assessed, and what each possible result would mean is explained in advance — before any sample is taken.
- Positive — a pathogenic variant was found. A surveillance plan follows, and a discussion about relatives.
- Negative — no known variant was found. This does not mean zero risk; it means this particular cause was not identified.
- Variant of uncertain significance (VUS) — something was found that we do not yet know to be harmful. It is not a basis for treatment decisions and is re-evaluated over time.
It concerns your family too
A positive result does not concern only you. Siblings and children generally have a 50% chance of carrying the same variant, and can be tested for it specifically.
The decision to be tested is personal and is not urgent. It is made after discussion, understanding the implications — and you always have the right not to want to know.
Frequently asked questions
Is genetic testing covered?
Coverage depends on the indication and the insurer, and changes over time. This is clarified before testing, as part of genetic counselling.
Can a commercial DNA test tell me the same thing?
Not reliably. Consumer tests usually check a limited set of variants and come without clinical interpretation. A “reassuring” result from one can be misleading.
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