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Testing your family for an inherited TP53 fault | CION Cancer Clinics
When one person is found to carry an inherited TP53 fault, their parents, brothers, sisters and children are usually offered a test for the same change. Each has a one in two chance of carrying it. This page explains who is tested and in what order, what each result means, and how families in Telangana share the news without pressure. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Who in the family should be tested for TP53?
- What does a TP53 test tell each relative?
- How does testing move through a TP53 family?
- What do the family testing terms mean?
- What does each result mean for a relative?
- What do families believe about testing relatives?
- What this page cannot tell you
- Common questions about testing a TP53 family
The short answer
Who in the family should be tested for TP53?
Once one person is found to carry an inherited TP53 fault, their parents, brothers, sisters and children are usually offered a test for that exact change. Each of them has a one in two chance of carrying it. Testing then moves outwards, one branch at a time, following whoever turns out to carry the fault.
Why the family is tested in a particular order
This step-by-step approach is called cascade testing. It saves money and worry, because it avoids testing people who cannot be at risk. If a brother tests negative, his children do not need a test at all, since he has nothing to pass on. If a parent carries the fault, that parent's side of the family is where testing goes next.
Why it matters more for TP53 than for most genes
An inherited TP53 fault can cause cancer in childhood and early adult life. Carriers are offered regular checks from a young age, and those checks aim to find tumours while they are small. A relative who does not know they carry the fault cannot benefit from them. That is the reason counsellors encourage families to share a TP53 result, gently but promptly.
Nobody can be made to take a test. Every adult relative decides for themselves.Relative by relative
What does a TP53 test tell each relative?
The same test answers a slightly different question for each person, depending on where they sit in the family tree.
Parents
Testing both parents shows which side of the family the fault came from. That tells everyone which aunts, uncles and cousins may need a test, and which side can relax.
If neither parent carries it, the fault may have started with the person tested.Brothers and sisters
Each has a one in two chance of carrying the fault if a parent does. A negative result for a sibling ends the question for their children too.
Children
For TP53, testing in childhood is usually discussed, because some checks begin in early childhood and may find tumours sooner. Parents decide with a counsellor, and there is no pressure to decide quickly.
Wider relatives
Aunts, uncles and cousins on the carrier's side come next, one branch at a time.
Testing usually follows
- The side the fault came from
- Whoever tests positive at each step
- Those planning a family or a marriage
Not sure whether this applies to you?
Ask an oncologistIn practice
How does testing move through a TP53 family?
The first result is confirmed
The first person found to carry the fault gets a written report naming the exact change. Every relative's test depends on that report, so keep copies safe.
Relatives are told
Most families share the news themselves, often with a letter from the counsellor that explains it in plain words. Asking for one in Telugu can help older relatives.
Each relative has their own counselling
Before testing, every adult talks through what a positive or negative result would mean for them, including marriage, work and insurance.
A known-fault test is done
A blood or saliva sample is checked for the family's one change. Relatives in other districts or abroad can often give samples near home.
Words you will hear
What do the family testing terms mean?
- Cascade testing
- Testing relatives step by step, following the fault through the family.
- First-degree relative
- A parent, brother, sister or child. They share half their genes with you.
- Known-fault test
- A test that looks only for the family's exact change. It is quicker and cheaper than the first test.
- Predictive test
- A test in someone who has never had cancer, to see whether they carry the family fault.
- True negative
- A relative who does not carry the known family fault. Their children cannot inherit it from them.
- De novo
- A fault that started with one person and was not inherited from either parent.
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Side by side
What does each result mean for a relative?
Carries the family fault
Does not carry it
Offered regular checks, including MRI scans
No extra checks for TP53 cancers
Radiation avoided where another option exists
Routine screening for age applies
Children have a one in two chance of carrying it
Children cannot inherit it from this parent
Family planning options can be discussed
Nothing further to test for
Commonly believed
What do families believe about testing relatives?
"My brother is healthy, so he does not need a test."
Carriers are healthy until they are not. The point of testing a well relative is to start checks before any cancer appears.
"It came from our father, so only the sons are at risk."
A TP53 fault passes to sons and daughters equally, from either parent. Women carriers also face a high breast cancer risk, so daughters matter just as much.
"If my sister tested negative, I must be negative too."
Each child's chance is separate, like a fresh coin toss. One sibling's result says nothing about another's.
"Telling relatives will ruin marriage prospects in the family."
That fear is real and common. A result is private information, and a counsellor can help you decide who needs to know, and when, without the whole community being told.
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault, or in what order your family should be tested. That depends on the shape of your family tree and who is willing to take part. What your specific variant means is a question for the counsellor who ordered the test.
It cannot settle when to test a child
Evidence for starting checks in childhood is growing, but studies are still modest in size. The right timing for your child is a decision you make with a counsellor and a paediatric oncologist, not one this page can make.
It cannot make a relative want to know
Some relatives will not want a test, and that is their right. Some change their mind years later, often around marriage or when their own children are born. Give them the letter, tell them where to go, and leave the door open. A counsellor can talk with them whenever they are ready.
Who this does not apply to
This applies only to families where an inherited TP53 fault has been confirmed on a germline test. If TP53 appeared only on a tumour report, relatives do not need testing on that basis.
Questions we are asked
Common questions about testing a TP53 family
Should my young children be tested for TP53?
It is usually discussed, because some checks for TP53 carriers begin in early childhood. Parents make this decision with a counsellor, weighing the benefit of early checks against the weight of knowing. There is no deadline, and it is fine to take time.
What if neither of my parents carries the fault?
Then the fault probably began with you. Your brothers and sisters are then at low risk, though a counsellor may still suggest a test. Your own children still have a one in two chance of inheriting it.
My parents have died. Can my relatives still be tested?
Yes. Once your own result names the fault, your brothers, sisters and children can be tested directly. Stored tissue from a parent's old surgery can sometimes show which side it came from, which helps decide whether aunts and cousins need testing.
How do I tell relatives I have not spoken to in years?
A short letter from the counsellor is often the easiest way. It explains the fault, the chance of carrying it and how to get tested, without you having to explain the science. You can send it by post or share a photo of it.
Can a relative abroad use a local lab?
Usually yes. They need a copy of the original report naming the exact change, so their lab tests for the right thing. A local genetics service can arrange the test and the follow-up checks where they live.
Does a negative relative need any checks at all?
Not for the family TP53 fault. They follow the same screening advice as anyone else their age. If there are cancers in the family that TP53 does not explain, their doctor may still suggest extra checks for those.
Will a positive result affect a relative's insurance?
India has no dedicated law on genetic discrimination in insurance, and the position has been argued in court rather than settled by statute. Relatives should raise this with the counsellor before testing, not after, and some arrange cover first.
Where does a family in Telangana start?
With the person whose report names the fault. Take that report to a genetic counsellor and list every close relative on both sides. Call the CION helpline if you are unsure where to begin, and someone will point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
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Sources
- GeneReviews (NCBI) — Li-Fraumeni Syndrome
- MedlinePlus Genetics — Li-Fraumeni syndrome
- NHS — Predictive genetic tests for cancer risk genes
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Deciding whether to test children for TP53The hardest family decision, looked at carefullyA de novo TP53 result with no family historyWhen neither parent carries the faultTP53 and family planningThe options for couples planning childrenTP53 testing cost in HyderabadWhat each relative's known-fault test usually costs
Talk to us
Not sure who in your family should be tested first?
Tell us who carries the fault and who else is in the family. We will help you reach a counsellor who can plan the order of testing with you. One helpline serves every CION centre.