Genetic testing and what it means for your family
The difference between testing the tumour and testing you, who is offered it, what a result does and does not change, and how relatives get tested.
5 min read · Part of Follow-Up & Surveillance
Written by The LifeAfterward editorial team from the sources listed at the end of this page.
Not individually reviewed by a clinician. This page is written from published clinical guidance, listed in full at the end, and is general information rather than medical advice — your own team knows your case. See our editorial standards.
Last checked against its sources · Last updated · Next check due
In short
- Two different tests share the word "genetic": one looks at the cancer, the other at you. Only the second says anything about your family.
- A result can change your own surveillance, your treatment options, and whether relatives are offered testing.
- "Variant of uncertain significance" is a common result and is not an answer — it should not drive decisions.
- Not finding a variant does not rule out inherited risk, especially where the family history is strong.
What this means
Genetic testing after cancer answers a different question from the one most people assume. It is rarely about why you got cancer, which usually cannot be answered. It is about whether a specific inherited change is present that changes what should happen next — for your screening, sometimes for your treatment, and for the people related to you.
Two tests, one word
- Tumour (somatic) testing
- Examines the cancer itself for changes that arose in those cells. Used to choose treatment. It says nothing about what you inherited or what your children might carry — although it can occasionally suggest an inherited change worth confirming.
- Germline testing
- A blood or saliva test that examines the genes you were born with. This is the one with implications for relatives.
- Pathogenic variant
- A change known to increase cancer risk — for example in BRCA1, BRCA2, or the mismatch repair genes associated with Lynch syndrome.
- Variant of uncertain significance (VUS)
- A change whose meaning is not yet known. It is not a diagnosis, should not trigger surgery or extra screening on its own, and is sometimes reclassified years later.
- No variant identified
- Nothing detectable was found in the genes tested. Reassuring, but not the same as no inherited risk — testing does not cover everything, and a strong family history still matters.
Who is usually offered germline testing
Criteria differ by country and change as evidence develops, so this is the shape of it rather than a rule — and if it was not discussed, it is entirely reasonable to ask whether you qualify.
- Cancer diagnosed unusually young.
- Several relatives with related cancers, or a relative with the same cancer at a young age.
- Certain diagnoses regardless of family history — ovarian cancer is the clearest example, and testing is recommended for essentially everyone diagnosed with it in many guidelines.
- More than one primary cancer in the same person.
- Particular tumour features, such as mismatch repair deficiency found on a bowel or womb cancer specimen.
- Male breast cancer, and certain prostate and pancreatic cancers.
- Ancestry associated with specific founder variants.
What a positive result actually changes
- Your surveillance — earlier or additional screening, sometimes with different imaging, for cancers you have not had.
- Risk-reducing options — surgery or medication, discussed over time rather than decided in one appointment.
- Treatment — some variants open specific drug options, and some tumour findings do the same.
- Your relatives — they can be offered predictive testing, which is far simpler once the family variant is known.
- Nothing else. It does not change how the cancer you already had is treated in most cases, and it is not a prediction that anyone else will get cancer.
Telling your family
- Genetics services routinely help with this, including letters written for you to pass on. Ask — most people do not know it is offered.
- Testing relatives usually starts with adults who would act on the result; children are generally not tested for adult-onset conditions.
- Relatives can decline. Some will, and that is their decision to make.
- Expect complicated reactions: guilt on your side, anger or avoidance on theirs. It is common and it usually settles.
- Counselling before and after testing is part of the service rather than an extra, for you and for them.
Insurance and employment rules vary
Whether a genetic test result can be used by insurers or employers differs substantially between countries, and some have moratoria or legal protections. Check the position where you live before testing if it matters to you — a genetics service will know.
What to ask your healthcare team
- Am I eligible for germline genetic testing, and has it been discussed?
- Was my tumour tested, and is that different from testing me?
- What would a result change — for my screening, my treatment, or my family?
- How long do results take, and who explains them?
- How do my relatives get tested if something is found?
- What is the position on insurance where I live?
Save questions to My Journey so you have them in the room, or use a ready-made list.
When to seek medical advice
Contact your healthcare team if you have:
- A family history that has changed — a new diagnosis in a close relative is a reason to ask again.
- A result you do not understand, particularly a variant of uncertain significance.
- Distress or guilt after a result — genetics services have counsellors for exactly this.
- Uncertainty about which extra screening you should now be having, and who arranges it.
If you are worried and unsure, contact your team anyway — they would far rather hear from you unnecessarily than late. What to do in an emergency.
Common questions
Does genetic testing tell me why I got cancer?
Usually not. Most cancers are not caused by a single inherited change, and testing looks for specific known variants rather than explaining causation. What a result can do is change your future screening, sometimes your treatment options, and whether relatives should be tested.
What is a variant of uncertain significance?
A genetic change whose effect is not yet known. It is not a diagnosis and should not on its own lead to risk-reducing surgery or extra screening. Classifications are reviewed as evidence accumulates, and some are later reclassified as harmless.
Sources
This page was written from the guidance below and checked against it on . Links are re-checked at each review — see our editorial standards.
- National Cancer Institute (US). Genetic testing for inherited cancer susceptibility syndromes
- ASCO (Cancer.Net). Survivorship
- National Comprehensive Cancer Network. NCCN Guidelines for Patients
- Cancer Research UK. Coping with cancer
- European Society for Medical Oncology. ESMO patient guides