ATM Gene Mutation: Cancer Risks, Screening, and Next Steps

ATM stands for Ataxia-Telangiectasia Mutated. It is a tumor suppressor gene located on chromosome 11 that plays a critical role in detecting DNA damage. When your cells experience a double-strand break in their DNA — one of the most dangerous types of DNA damage — the ATM protein is one of the first responders. It signals the cell to stop dividing and activates a network of repair proteins, including those produced by BRCA1, BRCA2, and CHEK2.

When someone carries a mutation in the ATM gene, this early detection system does not work as well. Cells with damaged DNA may continue to divide before repairs are made, and over time this can lead to cancer. ATM mutations are inherited in an autosomal dominant pattern for cancer risk, meaning you only need one mutated copy (from one parent) for it to affect your cancer risk.

The gene is named after the condition ataxia-telangiectasia (A-T), a rare childhood disorder caused by inheriting two mutated copies of ATM (one from each parent). This is called biallelic inheritance. Carriers with just one mutated copy — which is what hereditary cancer genetic testing typically identifies — have elevated cancer risk but do not develop A-T.

ATM mutations are more common than many people realize. Approximately 1 in 100 to 1 in 200 people carry a single ATM mutation, making it one of the more frequently identified moderate-risk genes on multi-gene panel tests. For a broader view of who should consider genetic testing and which genes are evaluated, see our guide on hereditary cancer screening.

This is the question most people ask first — and it deserves a clear answer. An ATM mutation raises your cancer risk, but it is classified as a moderate-risk gene, not a high-risk gene like BRCA1 or BRCA2. Most people with an ATM mutation will not develop cancer. However, the increased risk is real and warrants medical attention.

Here is how ATM cancer risks compare to the general population:

Breast cancer (women)

• General population lifetime risk: approximately 13%
• ATM mutation carriers: approximately 20–30% lifetime risk, depending on family history and the specific variant
• This is a moderate elevation — similar in magnitude to CHEK2
• A strong family history of breast cancer can push risk toward the higher end of this range

Pancreatic cancer

• ATM carriers have an estimated lifetime risk of approximately 5%, compared to roughly 1.7% in the general population
• Pancreatic cancer risk is the most clinically distinct feature of ATM mutations
• This risk is particularly relevant if there is a family history of pancreatic cancer

Ovarian cancer

• Some studies suggest a modest elevation in ovarian cancer risk for ATM carriers
• This association is less established than for BRCA genes and is still being studied

Prostate cancer (men)

• ATM carriers have approximately 2 times the general population risk, particularly for aggressive forms of prostate cancer
• General population lifetime risk: approximately 13%
• Research is ongoing, and individual risk depends on family history

Key takeaway: ATM carries moderate breast cancer risk — lower than BRCA1/2 but higher than average. Pancreatic risk is the most clinically distinct feature. Most carriers do not develop cancer, but enhanced screening is recommended because catching cancer early significantly improves outcomes.

ATM and BRCA are often mentioned together because they are all part of the DNA damage repair pathway. However, they carry very different levels of risk. Understanding the difference helps put an ATM result in perspective.

• Risk level: BRCA1 and BRCA2 are high-risk genes with lifetime breast cancer risks of approximately 50–72%. ATM is a moderate-risk gene with a lifetime breast cancer risk of approximately 20–30%.
• Pancreatic cancer: ATM carries a more distinct pancreatic cancer signal than BRCA2, with an estimated 5% lifetime risk. Pancreatic cancer risk is one of the most important clinical considerations for ATM carriers.
• Screening intensity: BRCA carriers typically start enhanced screening (MRI and mammogram) at age 25–30. ATM carriers generally begin annual mammograms at age 40, with breast MRI considered based on provider recommendation.
• Risk-reducing surgery: Prophylactic mastectomy is commonly discussed for BRCA carriers. For ATM carriers, risk-reducing surgery is generally not recommended unless there is also a strong family history of breast cancer.
• Ovarian cancer: BRCA mutations significantly increase ovarian cancer risk. ATM may modestly elevate ovarian cancer risk, but the evidence is less established.

Both ATM and BRCA genes are included in standard multi-gene panel tests for hereditary cancer. If you previously had targeted BRCA-only testing, you may want to discuss updated panel testing — which includes ATM — with your provider.

The goal of enhanced screening is not to prevent cancer, but to find it as early as possible if it develops. NCCN guidelines recommend the following for ATM carriers, though your provider may adjust these based on your personal and family history.

Women with an ATM mutation

• Annual mammogram starting at age 40 (or earlier if family history warrants it)
• Consider annual breast MRI based on provider recommendation and family history
• Clinical breast exam every 6–12 months
• Risk-reducing mastectomy is generally not recommended for ATM alone, but may be discussed if there is a strong family history of breast cancer

Men with an ATM mutation

• Discuss prostate cancer screening (PSA testing) with your doctor starting at age 40–45
• Discuss pancreatic cancer surveillance if there is a family history of pancreatic cancer

All ATM carriers

• Cascade testing: first-degree relatives (parents, siblings, children) should be offered genetic testing
• Discuss pancreatic cancer surveillance with your provider if there is a family history of pancreatic cancer
• Keep your healthcare team informed about your ATM status so they can tailor your care

Important: Screening recommendations vary based on your personal and family history. A licensed genetic counselor can help you build a personalized screening plan based on your specific variant and risk profile.

No diet can eliminate the cancer risk associated with an ATM mutation — the mutation is part of your DNA and is present from birth. However, general cancer risk-reduction strategies are especially important for ATM carriers because they can help lower your overall risk on top of enhanced screening.

Evidence-based strategies that apply to everyone, and are particularly relevant for ATM carriers:

• Maintain a healthy weight. Obesity independently increases breast and pancreatic cancer risk. For ATM carriers, this adds to an already elevated baseline risk.
• Stay physically active. Regular exercise is associated with reduced cancer risk across multiple cancer types.
• Limit alcohol. Even moderate alcohol consumption raises breast cancer risk. For ATM carriers, reducing or eliminating alcohol is a meaningful step.
• Do not smoke. Smoking increases cancer risk broadly and compounds hereditary risk.
• Eat a balanced diet. A diet rich in fruits, vegetables, and whole grains supports overall health, though no specific “ATM diet” has been studied or validated.

It is understandable to want to take action beyond screening. These lifestyle choices will not change your ATM mutation, but they can reduce your overall cancer risk and improve your health outcomes. These are population-level recommendations that apply to the general public and ATM carriers alike — not ATM-specific interventions. Discuss specific recommendations with your doctor or a registered dietitian.

If you have received a positive ATM genetic test result, here are the steps to take:

1. Share your results with your primary care doctor. Your physician, OB/GYN, or oncologist should know about your ATM status. This directly affects your screening plan and ongoing care.
2. See a licensed genetic counselor. ATM implications depend on your specific variant and family history. A genetic counselor can interpret your result, explain what it means for your risk, and help create a personalized management plan. See our guide on genetic counseling for cancer for more detail.
3. Tell your first-degree relatives. ATM mutations are inherited. Each parent, sibling, and child has a 50% chance of carrying the same mutation. Cascade testing can identify which relatives carry the variant so they can begin appropriate screening.
4. Begin appropriate screening. Follow the enhanced screening guidelines above, adjusted for your personal and family history. Discuss mammogram timing, breast MRI, and pancreatic surveillance (if relevant) with your provider.
5. Do not conflate ATM with BRCA. ATM is a moderate-risk gene. The risk is real, but it is lower than BRCA1 or BRCA2. Most ATM carriers never develop cancer. With appropriate screening and lifestyle choices, you are taking the most important steps to protect your health.

For general guidance on interpreting genetic test results, see our resource on understanding your genetic test results. If you have not been tested yet and want to find out whether hereditary cancer genetic testing is right for you, our free eligibility screener can help.

Want to find out if you qualify for hereditary cancer testing? Learn more about hereditary cancer testing eligibility.

NCCN recommends ATM testing as part of multi-gene panel testing for hereditary cancer syndromes. Testing is particularly indicated for individuals with a personal or family history of breast cancer, pancreatic cancer, or a known ATM mutation in the family. Carriers should be referred for enhanced breast screening.

ATM mutations follow autosomal dominant inheritance for cancer risk, meaning each first-degree relative has a 50% chance of carrying the same mutation. If both parents carry an ATM mutation, their children have a 25% chance of inheriting two copies, which would cause ataxia-telangiectasia. Cascade testing is recommended for all first-degree relatives to identify individuals who would benefit from enhanced cancer screening.