Medical Oncologist
CION Cancer Clinics
ALK and PHOX2B: testing the rest of the family | CION Cancer Clinics
Family testing for ALK or PHOX2B starts with the child who had neuroblastoma. If an inherited fault is found, both parents and every brother and sister can be tested for that one exact fault. Unlike most cancer genes, young children are tested early here, because the risk sits in the first years of life. This page explains who is tested, how, and what each result means. 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 ALK or PHOX2B?
- What does testing mean for each person in the family?
- How does family testing actually happen?
- The words you will meet, in plain language
- What does each result mean for a brother or sister?
- What families often get wrong about testing
- What this page cannot tell you
- Common questions about testing the family
The short answer
Who in the family should be tested for ALK or PHOX2B?
Start with the child who had neuroblastoma. If an inherited fault is found in that child, both parents and every brother and sister can then be tested for that one exact fault. If no fault is found in the affected child, testing the rest of the family usually adds nothing.
Why the affected child goes first
The child who had the tumour is the person most likely to carry a fault, if there is one. Testing them first tells the family whether there is anything to look for at all. Testing a well sibling first can give a reassuring result that means nothing, because nobody knew which fault to search for.
Why young children are tested here
For most cancer genes, testing waits until a child is an adult. ALK and PHOX2B are different. The risk of a tumour sits mainly in the first years of life, and regular checks in those years genuinely help. That is why brothers and sisters are usually tested while they are still small.
When the affected child has died
Families are sometimes asked about this long afterwards. A stored blood sample or a tissue block from an old operation can sometimes still be used. Ask the hospital that treated the child whether anything was kept.
Relative by relative
What does testing mean for each person in the family?
Once the family fault is known, each relative is tested for that one change. The reason for testing differs from person to person.
Parents
Testing the mother and father shows which side the fault came from, or whether it arose new in the child. A parent who carries it may never have been ill, which surprises many families.
Brothers and sisters
If a parent carries the fault, each child has a one in two chance of inheriting it. Siblings who test negative need no extra checks. Those who test positive are offered regular scans.
Babies born later
A new baby in the family can be tested soon after birth, so that checks can start early if needed.
Talk to a counsellor about
- Testing shortly after birth
- Testing during pregnancy
- Testing embryos during IVF
The wider family
If a parent carries the fault, their brothers and sisters may carry it too. Their young children are the ones who would benefit most from knowing.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually happen?
A counselling appointment first
A genetic counsellor draws the family tree and explains what a positive or negative result would mean. Nothing is tested until the parents understand the choices.
The affected child's sample
A blood sample is sent to a laboratory that reads ALK, PHOX2B and a few related genes. This first test takes the longest.
A targeted test for relatives
Relatives give a blood or saliva sample that is checked for the known family fault only. This is simpler, quicker and costs less than the first test.
Results given in person
Each result is explained face to face or on a call, never by text message. Children who carry the fault are then referred for a checking plan.
On your report
The words you will meet, in plain language
- Cascade testing
- Testing relatives one step at a time for a fault already found in the family.
- Carrier
- Someone who has the family fault. A carrier is not a patient and may never develop a tumour.
- Penetrance
- How often a fault actually leads to a tumour. For ALK it is incomplete, meaning many carriers stay well.
- Predictive test
- A test in someone who is well, to see whether they carry the family fault.
- Obligate carrier
- A relative who must carry the fault because of where they sit in the family tree, even without a test.
- Germline mosaicism
- A fault present in some of a parent's egg or sperm cells but not in their blood. Rare, but it explains some surprising families.
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Side by side
What does each result mean for a brother or sister?
Sibling carries the fault
Sibling does not carry it
Regular tummy scans and urine tests through early childhood
Ordinary childhood care, no extra checks
Any tumour is likely to be found early
Risk is the same as any other child
May pass the fault on as an adult
Cannot pass this fault on
Counselling again before their own family planning
No further testing needed for this fault
Commonly believed
What families often get wrong about testing
"We are both healthy, so neither of us can carry it."
Many parents who carry an ALK fault were never ill. Good health tells you nothing about carrier status. Only the blood test does.
"Our other children are too young to be tested."
For these genes, young is exactly when testing helps. The risk sits in early childhood, and checks that start early can find a tumour while it is small.
"Parents tested negative, so the other children are completely safe."
The risk is now very low, but a counsellor may still suggest testing siblings. Rarely, a parent carries the fault in some egg or sperm cells only.
"Being married to a relative made this happen."
ALK and PHOX2B faults pass from one parent. Marriage between relatives does not cause them or raise the chance of passing them on.
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault, or what a result means for a particular child. What your specific variant means is a question for the counsellor who ordered the test.
It cannot set a checking plan
How often a carrier child is scanned, and for how long, is decided by a paediatric oncologist who knows the gene and the family history. Plans differ, and the studies behind them are small because so few families have this fault.
Who this does not apply to
If testing of the affected child found no fault, this page does not apply to your family. The same is true if your child's neuroblastoma was a single tumour with no family history, and no test has been advised.
Relatives in another state or abroad can usually give a sample locally and have it sent to the same laboratory.Questions we are asked
Common questions about testing the family
Do all my children need to be tested?
Only if a fault has been found in the child who had neuroblastoma or in a parent. Then every brother and sister is usually offered a test, because each one has a one in two chance of carrying it when a parent does. If no fault is known, there is nothing to test for.
Is it safe to test a baby?
Yes. It needs only a small blood sample. For these genes, testing in babyhood is the whole point, because the tumour risk sits in the first years of life and checks can start straight away if the result is positive.
Why test the parents if the child has already been tested?
It shows which side of the family the fault came from. That decides whether aunts, uncles and cousins should be told. If neither parent carries it, the fault probably arose new in the child and the wider family is unlikely to be affected.
What if one parent refuses to be tested?
The children can still be tested directly. Nobody can be made to give a sample. A counsellor can meet the parent separately and explain what the result would and would not change, which often helps more than pressure from the family.
Can relatives in another district be tested?
Usually yes. Samples can often be collected close to home and sent to the laboratory. The counselling appointment can be done by video call, and in Telugu if that is easier, so relatives in other districts need not travel to Hyderabad.
Will a positive result affect a child's future marriage?
It is a fair worry in many Indian families. Whether and when to share a result is a private decision. A counsellor can help you think it through, and can meet the young person again when they are old enough to decide for themselves.
Does it matter for insurance?
India has no dedicated law on genetic discrimination in insurance, and the position is not settled. Raise it with your counsellor before testing, not afterwards. Some families arrange a child's cover before any predictive test is done.
Who arranges the tests?
A genetic counsellor or clinical geneticist, working with the paediatric oncologist who treated your child. Call the CION helpline if you are not sure where to start, and someone will guide 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
Medical Oncologist
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Sources
- GeneReviews (NCBI) — ALK-Related Neuroblastic Tumor Susceptibility
- MedlinePlus Genetics — Neuroblastoma
- MedlinePlus Genetics — ALK gene
- 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
Familial neuroblastoma: how rare is it?The clues that suggest it runs in your familyALK and PHOX2B positive: what happens nextThe checking plan for a child who carries the faultCascade testing: how a result moves through a familyThe general method, for any inherited genePrenatal diagnosis for a known family variantOptions for parents planning another pregnancy
Talk to us
Not sure who in your family should be tested?
Tell us who had neuroblastoma and what testing has been done so far. We will help you work out the next step for the rest of the family. One helpline serves every CION centre.