The short answer
Second cancers can arise from prior treatment, lifestyle and environmental factors, and genetic susceptibility. Follow-up care and a survivorship care plan help.
Nearly one in five cancers diagnosed today occurs in someone with a previous cancer diagnosis. That describes new diagnoses overall, not the odds for any one survivor.
NCI describes three categories: treatment, lifestyle and environmental factors, and genetic susceptibility.
Radiotherapy and some chemotherapies, such as alkylating agents and topoisomerase II inhibitors, can increase second cancer risk.
A survivorship care plan combines your treatment summary with follow-up recommendations.
On this page
Choose how you want to read this
The whole article, with every detail and caution.
This page is for people who have finished cancer treatment and want to understand their risk of a new, different cancer. It explains where that risk comes from and which parts you can act on.
Getting the scale right first
The National Cancer Institute says nearly one in five cancers diagnosed today occurs in a person who has had cancer before, and that there are more than 17 million cancer survivors. That statistic describes new diagnoses overall. It does not describe your own chance of a second cancer. Ask your care team what applies to you.
A second primary cancer is a new cancer. It is different from metastatic cancer, which is cancer that has spread from where it started.
Three sources of risk
NCI describes these main categories.
Treatment. NCI identifies radiotherapy and certain chemotherapies as established risk factors for later cancers. Ask your team which treatments you received and what they mean for you. Do not stop or change treatment on your own.
Lifestyle and environmental factors. NCI researchers are studying how obesity and tobacco use may influence second cancer risk. NCI's survivorship pages also note that smoking after cancer treatment can increase the chance of cancer at the same or a different site.
Genetic susceptibility. NCI says common genetic variations affecting DNA damage repair and other processes likely contribute to treatment-related cancer susceptibility. Ask your team whether genetic counseling makes sense for you.
What you can do
Talk with your care team about your follow-up care. NCI says people generally return for appointments every 3 to 4 months during the first 2 to 3 years after treatment, and once or twice a year after that. Your own schedule depends on your cancer type, treatments, and overall health.
If you smoke, ask your team about help to quit. See our page on quitting smoking.
Also follow NCI's advice: ask your doctor what cancer screenings you should have and when.
The document that ties it together
NCI describes a survivorship care plan as combining your treatment summary with follow-up recommendations. It may also include suggestions for emotional, social, or financial needs. A treatment summary should include your diagnosis, pathology reports, treatment details, warning signs, and possible long-term effects. If you do not have it in writing, ask for it.
Symptoms
NCI says to mention any symptoms, pain, or concerns that are new or that won't go away. Some problems may not show up until years after treatment. NCI says a new symptom does not automatically mean cancer has come back, but it is a reason to call your care team rather than wait. If a symptom is severe or sudden, call your care team right away or call 911.
Sources
Common questions
Does one in five survivors get a second cancer?
No. That figure means that nearly one in five cancers diagnosed today occurs in a person with a prior cancer history. It is not the individual chance of a second cancer. Ask your care team about your own situation.
Is a second cancer the same as a recurrence?
No, and the distinction matters. A recurrence is the original cancer returning. A second primary cancer is a new, biologically distinct cancer. They are investigated differently and treated differently, so if new disease is found it is reasonable to ask which one your team is dealing with.
Should I change or stop my treatment because of this risk?
No. Never stop or change treatment on your own. Talk with your care team about your questions.
Do I still need routine screening like mammograms and colonoscopy?
Ask your care team specifically which routine screenings you are due for, and whether your treatment history changes them.
Should I have genetic testing?
It depends on your cancer type, your age at diagnosis, and your family history. Ask your care team whether genetic counseling makes sense for you.
Questions to ask your doctor
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Written by: Cancer ExplainedSources last checked: 2026-10-16 what this meansLast updated: 2026-10-16Next planned review: 2027-07-30
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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, and this 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 then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team 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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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, and this 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 then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. 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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