The short answer
WHO estimates that about 37% of new cancer cases worldwide in 2022 were linked to preventable causes, but random cellular mutations mean cancer cannot always be prevented. Understanding this eliminates misplaced guilt.
WHO links about 37% of new cancer cases worldwide in 2022 to preventable causes, tobacco being the largest single one.
The rest cannot be prevented, because random copying errors occur among billions of daily DNA replications.
Someone who does everything right can still develop cancer, so guilt after a diagnosis is misplaced.
Choose how you want to understand this
The full explanation.
Can cancer always be prevented?
No. A large share of cancer can be prevented, but not all of it. Knowing that lifts a lot of misplaced guilt.
In 2026 the World Health Organization reported that about 37% of new cancer cases worldwide in 2022 were linked to preventable causes. That is close to four in ten. Tobacco was the largest single cause, at about 15% of new cases. Infections came next at about 10%, and alcohol at about 3%.
Why the rest cannot be prevented
Cancer starts when changes, called mutations, break the normal controls inside a cell. Cells then keep dividing when the body does not need them.
Some of those changes come from things you can act on, such as smoking. Some come from genes you inherited. Others simply happen as cells copy their DNA over a lifetime. As the National Cancer Institute puts it, some risk factors can be avoided and many cannot. Both smoking and an inherited gene can raise risk, but only smoking can be avoided.
So someone can do everything right and still get cancer. A diagnosis is not evidence that you failed.
What is worth doing anyway
The steps with the strongest evidence behind them are still worth taking. They include not smoking, HPV and hepatitis B vaccination, limiting alcohol, sun safety, and keeping up with recommended screening. Screening does not stop every cancer, but it can find some earlier or remove growths before they turn into cancer.
Be wary of health claims online. Red flags include 'miracle cures', secret treatments, and strict diets or supplements sold with the advice. Some supplements interact with cancer drugs, so tell your care team about anything you take.
Questions to ask your care team
- Which of my risk factors can I change, and which are genetic?
- Which screening tests fit my age and family history?
Sources
Words to know
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Common questions
Can someone who does everything 'right' still get cancer?
Yes. Normal cellular division involves billions of DNA replications daily, and random copying errors occur naturally over a lifetime.
What percentage of cancers are preventable?
WHO and IARC linked about 37% of new cancer cases worldwide in 2022 to preventable causes — tobacco at about 15%, infections at about 10% and alcohol at about 3%.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-08-13 what this meansLast updated: 2026-08-18Next planned review: 2027-07-23
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
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Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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