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CION Cancer Clinics
Testing the family for ATM: who, in what order, and why | CION Cancer Clinics
Once an ATM fault is found, each parent, brother, sister and adult child has a one in two chance of carrying it. They can be tested for that exact change quickly and cheaply. This page explains who to test first, what each relative stands to learn, why men matter as much as women, and why children usually wait until they are adults. 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 ATM?
- What does each relative stand to learn?
- How does family testing actually work?
- What do the family-testing terms mean?
- What does a relative's result mean for them?
- What this page cannot tell you
- What do families get wrong about testing relatives?
- Common questions about testing the family for ATM
The short answer
Who in the family should be tested for ATM?
Start with the closest adult relatives of the person who carries the fault: parents, brothers, sisters and grown-up children. Each of them has a one in two chance of carrying the same fault. Once someone tests positive, their own close relatives are offered testing next, and the circle widens step by step.
Why men matter as much as women
ATM is often talked about as a breast cancer gene, so brothers and fathers get left out. A man can carry the fault, never be ill, and pass it to a daughter. He may also be offered earlier prostate checks for himself. Leaving men off the list is one of the most common ways a family pattern is missed.
Why children usually wait
ATM mainly raises risk in adult life, and nothing changes for a child who tests positive. So testing usually waits until the child is an adult and can decide for themselves.
Why the whole family gains, even from a negative
A relative who tests negative for the family's fault did not inherit it and cannot pass it on. Their children can stop worrying about this gene altogether. In large joint families, that one result can lift the question from a whole branch of cousins at once.
Relative by relative
What does each relative stand to learn?
The same test answers slightly different questions for different people in the family.
Sisters and adult daughters
A positive result usually means breast screening starts earlier and may include an MRI. A negative result means routine screening for their age.
Brothers and adult sons
A positive result may bring earlier PSA discussions, and pancreas checks if the family history fits. It also tells them their own children could inherit it.
Parents
Testing a parent shows which side of the family the fault came from. That tells you whether aunts, uncles and cousins on that side should be offered testing too.
If both parents have died, the family history on each side often gives the counsellor a strong clue about where to look next.A partner, before children
This matters for a different reason. If both parents carry an ATM fault, a child can inherit two faulty copies and develop the childhood condition ataxia-telangiectasia.
Worth raising when
- The couple are related by blood
- Both families come from the same small community
- Either family has had a child with that condition
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually work?
The carrier shares the result
Your counsellor can give you a family letter explaining the fault in plain words. It can be printed or forwarded, including to relatives living abroad.
Each relative sees a counsellor
Every adult makes their own decision. The counsellor explains what a positive or negative result would mean for them before any sample is taken.
A test for the known fault
The lab looks only for the exact change found in your family. That makes it quicker and much cheaper than the first panel.
The result and a plan
A positive result comes with a screening plan. A negative one comes with the reassurance that this fault stops with them.
Words you will hear
What do the family-testing terms mean?
- Cascade testing
- Testing relatives one circle at a time, starting nearest the carrier and moving outwards as new carriers are found.
- First-degree relative
- A parent, brother, sister or child. They share about half your genes, which is why they are tested first.
- Known-fault test
- A test that looks for one specific change already found in the family, rather than reading the whole gene again.
- Dominant inheritance
- One faulty copy is enough to raise risk. It can pass from either parent to a son or a daughter.
- True negative
- A relative who does not carry a fault that is known to be in the family. It is the most reassuring result there is.
- Biallelic
- Having two faulty copies, one from each parent. For ATM this causes ataxia-telangiectasia rather than simply a raised cancer risk.
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Side by side
What does a relative's result mean for them?
They carry the family's fault
They do not carry it
Women start breast checks earlier
Routine screening for age applies
Each of their children has a one in two chance
Their children cannot inherit it from them
Their own close relatives are offered testing
Testing stops on their branch
A counsellor sets a personal plan
Other family history can still count
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault, or how to break the news in your own family. Every family talks about illness differently. A counsellor can help you plan who to tell first and what to say.
Who this does not apply to
It does not apply if the result in your family is a variant of uncertain significance. Relatives should not be tested for an uncertain change, because the answer would not mean anything yet. It also does not apply if ATM was found only in a tumour report. A tumour finding has to be confirmed in a blood test before anyone else is tested.
Where the evidence is thin
Risk estimates for ATM carriers come from smaller studies than those for BRCA, and they are still being refined. What your specific variant means is a question for the counsellor who ordered the test.
Relatives who tested negative can still have a raised risk from other parts of the family history. A negative result closes this one question only.Commonly believed
What do families get wrong about testing relatives?
"Only the women need testing, because it is a breast cancer gene."
Men carry and pass on ATM faults in exactly the same way. A brother's result matters for his daughters, and for his own prostate checks.
"We should test the children now, so we know."
Nothing changes for a child who tests positive, because checks start in adult life. Waiting lets them make the choice themselves, with full understanding of what it means.
"If I tested negative, my children still need a test."
They do not, for this fault. You cannot pass on a fault you do not carry, so the question ends with you.
"Telling relatives will spoil marriage prospects in the family."
The worry is real, and it deserves a careful conversation. But an ATM fault is common, raises risk moderately, and is managed with screening. Silence mostly means relatives miss checks that could protect them.
Questions we are asked
Common questions about testing the family for ATM
How do I tell my relatives?
Many families use the counsellor's family letter, which explains the fault in plain words and can be printed or shared on WhatsApp. Start with the closest relatives. Keep the message short: what was found, that it is manageable, and where they can get advice.
What if a relative does not want to be tested?
That is their right. Some people prefer not to know, or want time to think. Make sure they have the information, and let them know the offer stays open. Pressure rarely helps, and it can make the next conversation harder.
Do we have to tell a future spouse's family?
There is no legal duty to disclose an ATM result before marriage in India. Many families still wonder about it. A counsellor can help you think through what to share, with whom, and when, without anyone else deciding for you.
Should my partner be tested before we have children?
It is worth discussing, especially if you are related by blood or your families come from the same small community. If both of you carry an ATM fault, a child could inherit two faulty copies. A counsellor can explain the options before a pregnancy.
Can relatives living abroad be tested?
Yes. They can take the family letter and a copy of the original report to a genetics service where they live. The lab there needs the exact variant name to set up the known-fault test.
How much does a relative's test cost?
Much less than the first panel, because the lab looks for one change only. Costs vary between labs and are set out on our ATM test cost page. Counselling may be charged separately, so ask what is included before the sample is taken.
The relative who carried the fault has died. Can we still test?
If their report is available, yes. Relatives can be tested for the variant it names. If there is no report, a stored tissue block from an old surgery can sometimes be tested. Ask the hospital that treated them.
At what age can my children be tested?
Usually once they are adults and can give their own consent. Before then, nothing about their care would change. The exception is a child with symptoms of ataxia-telangiectasia, who is assessed by a specialist straight away.
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)
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Sources
- MedlinePlus Genetics — ATM gene
- GeneReviews (NCBI) — Ataxia-Telangiectasia
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- NCCN — Genetic/Familial High-Risk Assessment: Breast, Ovarian, Pancreatic, and Prostate
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
ATM testing cost in HyderabadWhat the known-fault test costs a relativeBiallelic ATM and ataxia-telangiectasiaWhy partner testing matters before childrenSurveillance for ATM carriersThe checks a relative who tests positive would haveATM positive: what happens nextThe first steps after your own positive result
Talk to us
Need help explaining an ATM result to your family?
A genetic counsellor can prepare a family letter and talk relatives through what testing would mean for them, in Telugu if they prefer. One helpline serves every CION centre.