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CION Cancer Clinics
Risk assessment: how your number is worked out | CION Cancer Clinics
Your cancer risk is estimated by entering your family history into a risk model, a tool built from studies of many families. The result is an estimate for people like you, not a prediction about you. This page explains the two different numbers you may be given, what information goes into them, and why most models need careful handling for Indian families. At CION Cancer Clinics in Hyderabad, our oncologists review your family history with you and guide you to the right genetic counselling and testing.
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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
- How is your cancer risk worked out?
- What information does the calculation use?
- How does the counsellor get from your family to a number?
- The risk words, in plain language
- What the number tells you, and what it does not
- Four things people assume about their risk number
- What this page cannot tell you
- Common questions about risk calculation
The short answer
How is your cancer risk worked out?
Your counsellor puts your family history into a risk model, a computer tool built from studies of many thousands of families. The model compares your family's pattern with those families and gives an estimate. It is a careful guess based on evidence, not a prediction about you.
You may be given two different numbers
The first is the chance that you, or someone in your family, carries an inherited gene fault. It helps decide whether a genetic test is worth doing. The second is your chance of developing a particular cancer over your lifetime. It helps decide what screening you need and when it should start. People often mix the two up, so ask which one you are being given.
Why the number can change
The estimate is only as good as the information behind it. A new diagnosis in the family, a relative's test result, or finding out that an aunt's "stomach cancer" was really ovarian cancer can all move the number up or down. It is worked out again whenever something important changes.
A risk estimate describes a group of people like you. It cannot say what will happen to you.What goes in
What information does the calculation use?
The model can only use what you tell it. Four kinds of information matter most.
Your family tree
Who had cancer, which cancer, and how old they were when it was found. Relatives without cancer count too, because they show how often cancer did not happen.
Most useful details
- Age at diagnosis for each relative
- Which side of the family
- Current age, or age at death
Your own history
Your age, any cancer or earlier biopsy you have had, and for breast risk, things like your periods, pregnancies and use of hormone treatment.
Tests already done in the family
If a relative has been tested, their result changes the calculation a great deal. A known family fault is the single most powerful piece of information.
Scan and tissue findings
Some models also use breast density from a mammogram, or features of a relative's tumour seen under the microscope. Your counsellor will ask for these reports if they help.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does the counsellor get from your family to a number?
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Your family tree is drawn
The counsellor draws your pedigree, at least three generations on both sides, marking every cancer and the age it was found.
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Key facts are checked
Where possible, relatives' diagnoses are confirmed from reports or hospital letters. A wrong cancer type can change the result noticeably.
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The right model is chosen
Different models suit different questions. Some are built for breast and ovarian cancer, others for bowel cancer. Some estimate the chance of a gene fault, others the chance of cancer.
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The details are entered
The model compares your family's pattern with the families it was built from, and produces an estimate.
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The counsellor sense-checks it
A model misses things a person notices, such as a very small family or marriage between relatives. The counsellor weighs the number against what they know, then explains it to you in words.
Words you may hear
The risk words, in plain language
- Lifetime risk
- The chance of developing a particular cancer at some point in your life, usually counted up to old age.
- Carrier probability
- The chance that you carry an inherited gene fault. It is used to decide whether testing makes sense.
- Risk model
- A computer tool that turns family history into an estimate, based on studies of large numbers of families.
- Tyrer-Cuzick
- A model often used to estimate breast cancer risk. It includes hormonal and family factors. It is also called IBIS.
- BOADICEA and CanRisk
- A breast and ovarian cancer model, and the online tool that runs it. It can include gene results and breast density.
- Manchester score
- A simple points system that adds up family cancers to estimate the chance of a gene fault linked to breast and ovarian cancer.
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Side by side
What the number tells you, and what it does not
It can tell you
It cannot tell you
Whether a genetic test is likely to be useful
Whether you carry a fault
Whether your screening should start earlier
Whether you will develop cancer
How you compare with the general population
When cancer might appear
Which relatives might be at higher risk
What your relatives should decide
Commonly believed
Four things people assume about their risk number
"A high number means I will get cancer."
Even a high estimate means many people in the same group never develop cancer. It is a reason to be watched more closely, not a forecast.
"A low number means I never need screening."
A low estimate usually means ordinary screening for your age applies. It does not remove the need for the routine checks everyone is offered.
"The computer knows my family better than I do."
The model knows only what was entered. Your memory of who had what, at what age, is the most important input it has. Gaps and guesses weaken the result.
"My number will never change."
It changes as you age and as your family's story changes. A new diagnosis or a relative's test result can move it a long way in either direction.
Being straight with you
What this page cannot tell you
It cannot calculate your risk. That needs your full family tree, entered by someone trained to use the models and to spot what they miss. Online calculators aimed at the public are not a substitute.
The models were mostly built outside India
Most risk models were developed from families in Europe and North America. Studies checking how well they work for Indian families are still small. Marriage between relatives, large joint families and missing records can all affect accuracy. A good counsellor tells you this plainly and treats the number as a guide.
Who this does not apply to
If a gene fault has already been found in you, a general model is no longer the main tool. Your risk is then guided by that specific gene. What your specific variant means is a question for the counsellor who ordered the test. And most people with one older relative with cancer do not need a formal calculation at all.
If a number you were given does not make sense, ask for it to be explained again, in words.Questions we are asked
Common questions about risk calculation
Is my risk number the same as my chance of carrying a gene fault?
No. One number is the chance you carry a fault. The other is the chance you develop cancer over your life. They answer different questions and can be quite different sizes. Ask your counsellor which one they are giving you.
Why did two clinics give me different numbers?
They may have used different models, or been given slightly different family details. Neither is necessarily wrong. Ask each which model was used and what information went in, then compare the inputs rather than the outputs.
Can I calculate my own risk online?
Some public calculators exist, but they are simplified and easy to use wrongly. The professional tools need details that are hard to enter correctly without training. Use an online result only as a reason to ask for proper assessment.
Does my father's side count?
Yes, fully. Faults linked to breast and ovarian cancer can pass through men who never become ill. Leaving out the father's side is one of the most common reasons a family's risk is underestimated.
What if I do not know my relatives' diagnoses?
Give what you know and say what you are unsure of. Your counsellor can work with gaps, and may help you get records. An honest "I do not know" is far better than a guess the model treats as fact.
Does marriage within the family change the calculation?
It can, and most models do not account for it well. Tell your counsellor if your parents or grandparents were related by blood. It matters more for some conditions than others, and they will explain how it applies.
Will the number decide whether I get tested?
It is a big part of that decision, alongside testing guidelines and your own wishes. A clearly raised estimate usually supports testing. A borderline one leads to a discussion rather than an automatic yes or no.
Should my number be recalculated later?
Yes, if anything important changes. That means a new diagnosis in the family, a relative's test result, or reaching an age when screening advice shifts. Tell the clinic, and ask whether your estimate should be updated.
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
- National Cancer Institute — Cancer Genetics Risk Assessment and Counseling (PDQ)
- University of Cambridge — CanRisk: the BOADICEA risk model tool
- Cancer Research UK — Family history and cancer risk
- MedlinePlus Genetics — What does it mean to have a genetic predisposition to a disease?
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
Risk assessment models explainedTyrer-Cuzick, BOADICEA and Manchester comparedWhat a lifetime risk percentage actually meansTurning the number into something you can useDrawing the pedigreeHow your family tree is put on paperVerifying family cancer history with recordsWhy checked facts give a better estimate
Talk to us
Would you like your family history assessed properly?
Bring what you know about your relatives and we will arrange an assessment with a qualified counsellor. One helpline serves every CION centre.