Medical Oncologist
CION Cancer Clinics
POLE and POLD1 faults: which cancers, and how much risk | CION Cancer Clinics
A proofreading fault in POLE or POLD1 mainly raises the risk of bowel polyps and bowel cancer, sometimes from a young age. POLD1 faults also raise the risk of womb lining cancer, and POLE faults the risk of growths in the duodenum. The condition is rare and studies are small, so exact figures are uncertain. This page sets out what is known and what is not. 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
- Which cancers does a POLE or POLD1 fault raise?
- Where does the risk sit?
- How does a doctor estimate the risk for you?
- What do the words on a POLE or POLD1 report mean?
- How do POLE and POLD1 differ?
- What do families misunderstand about POLE and POLD1?
- What can this page not tell you?
- Common questions about POLE and POLD1 risk
The short answer
Which cancers does a POLE or POLD1 fault raise?
Mainly bowel cancer. A proofreading fault in either gene leads to a build-up of polyps in the bowel, and some can turn into cancer if they are not removed. The risk is substantially higher than in the general population, and cancers have been seen at unusually young ages.
The name doctors use
The condition is called polymerase proofreading-associated polyposis, often shortened to PPAP. Polymerase is the enzyme that copies DNA. Proofreading is its built-in check for errors. Polyposis means many polyps. Only faults in the proofreading part of each gene cause it.
Why the numbers are uncertain
PPAP was first described just over a decade ago and is rare. Most of what is known comes from a small number of families worldwide, many found because they already had a lot of cancer. Risk figures from such families can overstate the risk for everyone else. Families found through routine testing, with little cancer in their history, may turn out to have lower risks than the early reports suggest.
A raised risk is not a diagnosis. Regular checks exist to catch changes early.Organ by organ
Where does the risk sit?
The evidence is strongest for the bowel and weakest for the organs at the end of this list.
The bowel
The main risk for both genes. Many carriers develop a modest number of polyps, not the hundreds seen in some other syndromes. Bowel cancer is the most common cancer reported in carriers. In some families polyps have appeared in the teenage years, so checks may begin earlier than ordinary screening.
The womb lining
Reported most often in women carrying POLD1 faults, and also seen with POLE. In POLD1 families it is the second most common cancer after bowel cancer.
The duodenum
The duodenum is the first part of the small bowel, just past the stomach. POLE carriers can develop polyps and occasionally cancer there, which is why upper gut checks are often added.
Other organs
Other cancers have been reported in a few families. It is not yet clear whether they are truly linked or chance findings.
Reported, not proven
- Brain tumours
- Ovarian cancer
- Breast cancer, with POLD1
Not sure whether this applies to you?
Ask an oncologistWorking out your risk
How does a doctor estimate the risk for you?
Confirm the change sits in the proofreading region
Only changes in the proofreading part of POLE or POLD1 are linked to PPAP. A change elsewhere in either gene usually does not carry the same risk.
Check how the change has been classified
Many proofreading variants are new or rare. Laboratories follow specific rules to decide whether one is truly harmful, and some stay uncertain.
Look at the family pattern
Who had polyps or cancer, in which organ and at what stage of life all shape the plan. A family with womb cancer may be advised differently from one with only bowel polyps.
Match the plan to the gene
POLE and POLD1 share a bowel plan but differ in the extras. The counsellor then sets out which checks start when, and why.
On your report
What do the words on a POLE or POLD1 report mean?
- Polymerase
- The enzyme that copies DNA when a cell divides. POLE and POLD1 each make the main part of one.
- Exonuclease domain
- The proofreading part of the enzyme. It removes wrong letters as soon as they are added.
- PPAP
- Polymerase proofreading-associated polyposis. The inherited condition caused by a proofreading fault in either gene.
- Oligopolyposis
- A modest number of bowel polyps. More than usual, but far fewer than in classic polyposis.
- Ultramutated tumour
- A tumour carrying a very large number of DNA changes, typical when proofreading has failed.
- Germline
- Present in every cell from birth and able to be passed on. Somatic means found only in the tumour.
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Side by side
How do POLE and POLD1 differ?
POLE
POLD1
Found in more of the known families
Rarer, with fewer families studied
Bowel polyps and cancer are the main risk
Bowel polyps and cancer are the main risk
Duodenal polyps more often reported
Duodenal findings less often reported
Womb lining cancer reported
Womb lining cancer more often reported
Brain tumours reported in a few families
Brain and breast cancers reported in a few families
Commonly believed
What do families misunderstand about POLE and POLD1?
"My womb cancer has a POLE mutation, so my family is at risk."
Usually not. POLE changes are common inside womb cancers themselves and are not inherited. A tumour result says nothing about relatives until a blood test shows the change is in every cell.
"POLE is just another Lynch gene."
It is not. Lynch syndrome comes from faults in the mismatch repair genes. PPAP comes from faults in the copying enzyme's own proofreading. The tumours can look alike, but the genes, tests and plans differ.
"Any change in POLE or POLD1 means PPAP."
Only changes in the proofreading region are linked to PPAP. A change elsewhere in either gene is usually treated very differently, and is often reported as uncertain.
"The risk figures I found online apply to me."
Published figures come from small numbers of families, many with heavy cancer histories. They may overstate the risk for a family found by chance. Your counsellor will explain how uncertain the numbers are.
Being straight with you
What can this page not tell you?
It cannot tell you your own risk. The exact variant, whether it sits in the proofreading region and your family pattern all change the picture. What your specific variant means is a question for the counsellor who ordered the test.
Where the evidence is thin
PPAP is rare and was described only recently. Studies so far are small, and figures for any organ other than the bowel are uncertain. We would rather say that plainly than give you a number that may not hold. Very few families from India have been described in published studies, so we cannot yet say whether the pattern here matches the pattern seen abroad.
Who this does not apply to
Most people do not need POLE or POLD1 testing. A POLE change found only in a tumour belongs to treatment planning and is covered under targeted therapy. If no one in the family has had many polyps, or bowel or womb cancer young, this condition is unlikely.
Questions we are asked
Common questions about POLE and POLD1 risk
Are POLE and POLD1 part of a standard gene panel?
Many bowel cancer and polyposis panels now include both genes, but not all. If a relative had many polyps or bowel cancer young and earlier testing found nothing, ask whether POLE and POLD1 were included. Your counsellor can check the panel list.
Does a POLE fault raise cancer risk in men?
Yes. Bowel and duodenal risks apply to men and women alike. Womb lining cancer applies only to women, and the other reported cancers are too uncertain to separate by sex. Men should be included in the family tree and in testing.
Can a child inherit a POLE or POLD1 fault?
Each child of a carrier has a one in two chance of inheriting it, and sons and daughters are equally likely to. A child who does not inherit the fault cannot pass it on and does not need the extra checks.
How young can cancer appear?
Bowel cancer has been reported in teenagers in a few families, which is why some experts suggest starting bowel checks early. Most carriers are not affected that young. The starting point for checks is set by your specialist, based on the gene and the family.
Are POLE tumours treated differently?
They can be. Tumours with failed proofreading carry many DNA changes and can respond to immunotherapy. Those decisions rest on tests of the tumour itself and are made by the treating oncologist, not from the family result alone.
Does PPAP raise the risk of breast cancer?
A link has been suggested for POLD1 in a small number of families, but it is not established. Most guidance does not add extra breast checks on the strength of a POLE or POLD1 result alone. Your counsellor will tell you if your family history changes that.
My report shows a POLE variant of uncertain significance. What now?
It means the laboratory cannot yet say whether the change is harmful. It should not change your care or lead to extra procedures. Care is planned on your family history, and the variant may be reclassified as more families are studied.
Where do I start if a relative has PPAP?
Ask for a copy of their report showing the exact variant. Take it to a genetic counsellor or gastroenterologist, who can arrange a test for that change. Call the CION helpline if you are unsure who to see, 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)
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Sources
- Familial Cancer — The clinical features of polymerase proof-reading associated polyposis (PPAP) and recommendations for patient management
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ)
- NCBI MedGen — Polymerase proofreading-related adenomatous polyposis
- Genome Medicine (PMC) — Recommendations for the classification of germline variants in the exonuclease domain of POLE and POLD1
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
Polymerase proofreading-associated polyposisThe condition itself, explained from the startSurveillance for POLE and POLD1 carriersWhich checks are offered, and whyTesting the family for POLE and POLD1Who should be tested once a fault is foundThe POLE and POLD1 genes: what they doHow DNA proofreading works in the first place
Talk to us
Has someone in your family been found to carry POLE or POLD1?
Tell us what the report says and who in the family has had polyps or cancer. We will help you reach a counsellor who can explain what it means for you. One helpline serves every CION centre.