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APC I1307K: a low-risk variant that is often misread | CION Cancer Clinics
APC I1307K is a small change in the APC gene that slightly raises the chance of bowel cancer. It is not familial adenomatous polyposis, it does not cause hundreds of polyps, and it rarely calls for more than a colonoscopy plan that starts a little earlier. This page explains what the variant is, why reports cause alarm, and what it does and does not change. 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
- Is APC I1307K the same as having FAP?
- Who carries I1307K, and what does it raise?
- What usually happens once I1307K is found?
- The words beside I1307K, in plain language
- How does I1307K differ from a classic APC fault?
- Four things people assume about I1307K, and what is true
- What this page cannot tell you
- Common questions about APC I1307K
The short answer
Is APC I1307K the same as having FAP?
No. I1307K is a single spelling change in the APC gene that nudges up the chance of bowel cancer by a modest amount. Familial adenomatous polyposis, or FAP, is caused by faults that break the gene outright and fill the bowel with polyps. The two share a gene name and very little else.
Why the report causes so much alarm
Many families search the gene name, land on pages about FAP, and read about hundreds of polyps and surgery to remove the bowel. None of that applies to I1307K. The laboratory reported it because it does carry some extra risk, and listing it helps your doctor plan checks. It is a note about risk, not a diagnosis of a syndrome.
What the variant actually does
The change swaps one letter in a stretch of DNA that is already repetitive. The swap makes that stretch slippery when cells copy themselves, so a second fault is a little more likely to appear in a bowel cell over a lifetime. The gene itself still works. That is why the extra risk is small and why polyps do not appear in large numbers.
I1307K is a low-risk finding. Most people who carry it never develop bowel cancer.Four facts at a glance
Who carries I1307K, and what does it raise?
A plain summary you can forward to the rest of the family.
Who usually carries it
The variant is most common in people of Ashkenazi Jewish ancestry, where it passed down from a shared ancestor. Outside that group it is uncommon, and studies in Indian families are few. It still turns up on Indian reports because broad gene panels look for it.
What it raises
A modestly higher chance of bowel cancer than the general population. Some studies suggest the effect is stronger when bowel cancer already runs in the family. Links to other cancers have been looked for and are not established.
What it does not do
It does not cause the carpet of polyps seen in FAP, and it is not linked to the other features classic APC faults can bring.
Not linked to
- Polyposis, meaning very many polyps
- Desmoid tumours, eye marks or dental changes
- Preventive bowel surgery
Who this does not apply to
If your report names a different APC change, this page is not about you. Classic and attenuated FAP need a very different plan. Ask your counsellor which kind your report shows.
Not sure whether this applies to you?
Ask an oncologistAfter the report
What usually happens once I1307K is found?
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The counsellor confirms the exact variant
Your report is checked to make sure the change is I1307K and not another APC fault with a similar-looking code. That difference matters more than anything else on the report.
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Your family history is drawn out
Who had bowel cancer, polyps or other cancers, on both sides, and at what age. A strong family history can shape the plan more than the variant itself does.
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A colonoscopy plan is agreed
Guidelines generally suggest carriers begin colonoscopy somewhat earlier than the general population and repeat it at routine intervals. The frequent checks used in FAP are not needed.
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Close relatives are told
Brothers, sisters and grown children can choose to be tested. Some families decide that a colonoscopy plan based on the shared family history is simpler than testing everyone. Both routes are reasonable.
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The plan is reviewed if anything changes
A new cancer in the family, or polyps found at colonoscopy, can shift the plan. Otherwise it simply continues, with no treatment and no extra tests.
On your report
The words beside I1307K, in plain language
- APC
- The gene that acts as a brake on cell growth in the lining of the bowel.
- I1307K
- A code for one letter change in the APC gene. It names the exact spot and the swap.
- Low-penetrance variant
- A change that raises risk a little, so most people carrying it never develop the cancer linked to it.
- Risk allele
- Another way some laboratories describe a low-risk variant. It means the same thing.
- Founder variant
- A change passed down from one shared ancestor, which is why it clusters in one community.
- Heterozygous
- You carry one copy of the change and one ordinary copy. Almost every carrier is reported this way.
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Side by side
How does I1307K differ from a classic APC fault?
APC I1307K
Classic APC fault (FAP)
A modest rise in bowel cancer risk
A very high bowel cancer risk without care
Polyps in ordinary numbers, if any
Hundreds of polyps, often from the teenage years
Colonoscopy starts somewhat earlier
Bowel checks start in childhood and are frequent
No preventive bowel surgery
Surgery to remove the bowel is usually planned
Commonly believed
Four things people assume about I1307K, and what is true
"My report says APC, so I have FAP."
FAP is caused by changes that stop the gene working. I1307K leaves the gene working and only makes a nearby stretch of DNA more error-prone. Your counsellor can confirm which kind of change you carry in a single conversation.
"Our family is not Jewish, so the result must be a mistake."
Laboratories confirm what they report. The variant is simply less common in other communities, not absent. It can appear in any family, and it means the same thing wherever it is found.
"I need my bowel removed to be safe."
No guideline recommends preventive bowel surgery for I1307K. A colonoscopy plan finds and removes any polyps early, which is the protection this variant needs.
"My children must be tested now."
I1307K carries no childhood risk, so nothing needs deciding while they are young. As adults they can choose testing, or simply follow a colonoscopy plan based on the family history.
Being straight with you
What this page cannot tell you
It cannot tell you what your own risk is. That depends on your age, your family history and whether you carry anything else on the panel. A genetic counsellor weighs all of it together. What your specific variant means is a question for the counsellor who ordered the test.
It cannot say how strong the effect is in Indian families
Most research on I1307K comes from Jewish communities in Israel and North America. Studies in South Asian families are small, and nobody can yet say with confidence whether the risk is the same here. Your plan is built on the best evidence available, which is not the same as perfect evidence.
Who this does not apply to
If your report shows an APC change that stops the gene working, or mentions polyposis, this page does not describe you. Read about classic and attenuated FAP instead, and speak to a counsellor soon. If your report shows no APC change at all, I1307K is not something you need to think about.
If you are unsure which kind of APC change your report shows, call the helpline and someone will arrange for it to be read properly.Questions we are asked
Common questions about APC I1307K
Does APC I1307K mean I will get bowel cancer?
No. It raises the chance modestly, and most people who carry it never develop bowel cancer. What it does is give your doctor a reason to start colonoscopy a little earlier, so any polyp is found and removed long before it could turn into cancer.
How often will I need a colonoscopy?
Most carriers need colonoscopy at routine intervals, starting somewhat earlier than the general population. The exact age and gap depend on your family history. If a close relative had bowel cancer young, the checks will be closer together. Your gastroenterologist sets the schedule after the first colonoscopy.
Should my brothers and sisters be tested?
They can be. If a parent carries it, each brother or sister has a one in two chance of carrying it too. Some families skip testing and give everyone a colonoscopy plan based on the family history. Both routes protect people, and the counsellor will help you choose.
Does I1307K raise the risk of breast or other cancers?
Early studies looked for links to breast and other cancers. The evidence is weak and inconsistent, and no guideline changes breast or other screening because of I1307K alone. Ordinary screening for your age and family history applies.
Is I1307K the same as attenuated FAP?
No. Attenuated FAP is a milder form of polyposis caused by other APC faults, usually with dozens of polyps rather than hundreds. I1307K does not cause polyposis at all. If your report or colonoscopy mentions many polyps, ask about attenuated FAP specifically.
Will this result affect a marriage in the family?
It should not. I1307K is a low-risk finding that needs no treatment, and it is not a syndrome. Families sometimes worry that any gene result will be held against a son or daughter. A counsellor can help you decide who needs to know and how to explain it simply.
Will a test result affect my insurance?
India has no dedicated law on genetic discrimination in insurance, and the question has been argued in court rather than settled by statute. Disclosure depends on the policy wording. Raise it with your counsellor, and read any proposal form carefully before answering a question about genetic tests.
Can I have this explained in Telugu, near my district?
Yes. The colonoscopy plan for I1307K can be followed close to home, and the counselling conversation can happen in Telugu. Call the CION helpline and describe your report. Someone will tell you which centre is nearest and whether you need a counsellor first.
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
- GeneReviews (NCBI) — APC-Associated Polyposis Conditions
- MedlinePlus Genetics — APC gene
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ)
- NCCN — Genetic/Familial High-Risk Assessment: Colorectal, Endometrial, and Gastric
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
The APC gene: what it does and why it mattersWhat the gene does when it works normallyAttenuated FAP and a milder APC resultWhen the polyp count is lower, but it is still polyposisSurveillance for APC carriersHow bowel checks are planned for APC resultsTesting the family for APCWho in the family might choose to be tested
Talk to us
Worried that an APC result means FAP?
Send us the report and we will arrange for a genetic counsellor to explain what kind of APC change it shows. Most I1307K results need only a colonoscopy plan. One helpline serves every CION centre.