Survivorship: During and After Treatment

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Second Cancers

While some cancer survivors stay cancer-free for the rest of their lives, it’s possible for others to develop a new, different cancer after the first one has been treated. This is different from the cancer coming back (recurrence).

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What are second cancers?

A second cancer (also called secondary malignancy or second primary cancer) is a new cancer that's unrelated to any previous cancer diagnosis. It's a completely different type of cancer. A second cancer is different from a cancer recurrence, which is when the same type of cancer that a person had before comes back.

Second cancers can:

  • Be in the same organ or area of the body as the first cancer. For example, someone who was treated for a certain type of colorectal cancer can get another type of colorectal cancer as a second cancer.
  • Develop in another organ or tissue.

Second cancers aren’t common. The rate at which they occur varies based on things like:

  • Age of first diagnosis
  • Treatment received
  • Type of cancer

What are symptoms of a second cancer?

Symptoms of a second cancer vary based on the type of cancer and where it is located. General symptoms may include:

  • Feeling tired
  • Having a sore that does not heal normally
  • Having a cough or hoarse voice that does not go away
  • Loss of appetite, difficulty digesting your food, or difficulty swallowing
  • A lump, discharge, bleeding, or thickening in a certain spot
  • Feeling like your bones ache
  • Headaches and vision changes

If you notice any of these changes, talk with your cancer care team as soon as possible.

Who is at risk for second cancers?

It’s not always clear what causes a second cancer or who is most at risk of getting one. Some second cancers have the same or similar risk factors as a first cancer. But the risk is shown to be higher for people:

For others, the risk for a second cancer may be lower or simply isn't known.

Things that can raise your risk for a first cancer, like lifestyle habits, environmental exposures, family history, and genetics, may also increase your risk for a second cancer.

The age you have a first cancer can matter, too. For example, survivors of childhood cancers can develop second cancers from some effects of treatment or because of hereditary or genetic problems. Also, because a person's risk for cancer in general goes up as they age, an unrelated new cancer may develop later in a cancer survivor's life.

Some cancer treatments can raise the risk of getting a second cancer later on. Because chemotherapy and radiation have been used as cancer treatments for a longer time, we know more about how they increase risk for second cancers than newer treatments, like targeted therapy or immunotherapy.

Radiation therapy has been known as a possible cause of cancer for many years. Much of what we know about its health effects comes from studying survivors of atomic bomb blasts in Japan. We have also learned from people whose jobs exposed them to radiation and from people who received radiation therapy for cancer and other diseases.

Radiation uses high-energy particles or waves to destroy cancer cells. While it is carefully aimed at the cancer, it can also damage the DNA of nearby healthy cells, which may increase the risk of second cancers.

Leukemia and myelodysplastic syndrome

Past radiation exposure is one risk factor for most kinds of leukemia, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and acute lymphoblastic leukemia (ALL). Myelodysplastic syndrome (MDS) has also been linked to past radiation exposure. The risk of these diseases after radiation treatment for cancer depends on a number of factors, such as:

  • How much of the bone marrow was exposed to radiation
  • The amount of radiation that reached the bone marrow
  • The radiation dose rate (how much was given in each dose, how long it took to give the dose, and how often it was given)

Most often, these cancers develop within several years of a person's radiation treatment. Then the chance of developing these cancers slowly declines over time.

Solid tumors

There is also a risk for other cancers, which are mostly solid tumors, after having radiation therapy. Most of these cancers develop 10 years or more after treatment. Examples of second cancers following radiation therapy include breast, lung, and thyroid cancer, or bone and soft tissue sarcomas.

The effect of radiation on the risk of developing a solid tumor depends on factors such as:

  • The age of the person when they were treated with radiation. Those that were treated as children or a young adult tend to have a higher risk for a second cancer. For example, young adults treated with radiation for Hodgkin disease are at greater risk for breast cancer later in life.
  • The dose of radiation. In general, the risk of developing a solid tumor goes up as the radiation dose increases. Some cancers require larger doses of radiation than others, and certain treatment techniques use more radiation.
  • The area treated. Cancers tend to develop in or near the area that was treated with radiation. Certain organs, such as the breast and thyroid, seem to have a higher risk for developing cancers after exposure to radiation than other organs.

Chemotherapy (chemo) uses medicines to destroy cancer cells. Like radiation therapy, it can also affect healthy cells, causing DNA changes that may lead to second cancers. The timing of these second cancers varies based on the type of chemo, usually occurring within 10 years after treatment. Some can occur decades later.

Some types of chemo drugs have been linked with different kinds of second cancers. The cancers most often linked to chemo are myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Sometimes, MDS occurs first, then turns into AML. Acute lymphocytic leukemia (ALL) has also been linked to chemo. Chemo is known to be a greater risk factor than radiation therapy in causing leukemia.

The risk gets higher with higher drug doses, longer treatment time, and higher dose-intensity (more drug given over a short period of time). Chemotherapy agents that have an increased risk for second cancers include:

  • Alkylating agents (such as busulfan, chlorambucil, cyclophosphamide, and melphalan) including platinum-based drugs (such as cisplatin and carboplatin)
  • Anthracyclines (such as doxorubicin and epirubicin)
  • Topoisomerase II inhibitors (such as etoposide, mitoxantrone, and teniposide)

Some drugs used to treat cancer are called targeted therapies because they are designed to find and attack certain changes, mutations, or substances on or in cancer cells.

Vemurafenib and dabrafenib are drugs that target the BRAF protein. They are used to treat melanoma and are being studied for use in other cancers. People taking these drugs have a higher risk of squamous cell carcinomas of the skin.

Targeted therapies are newer compared to other treatments, so not as much is known about the risk of second cancer yet. In general, they are believed to pose a smaller risk for second cancers.

Immunotherapies are treatments that uses the body’s immune system to find and attack cancer cells. Like targeted therapy, it is a newer type of cancer treatment and for this reason, not as much is known about its second cancer risks. Immunotherapy is not a single type of treatment. It includes different types of therapies, each working in its own way to treat cancer. One type of immunotherapy drug called lenalidomide, which is an immunomodulator used to treat multiple myeloma, has been found to have an increased risk of leukemia, MDS, and solid tumors.

But other types may reduce the risk. Some research suggests that immune checkpoint inhibitors, used to treat cancers such as lung cancer and melanoma, may actually reduce the risk of second cancers. This may be due to their effect on the body’s immune system to better find and attack cancer cells. More research is needed to determine how long this effect may last.

Another type of immunotherapy, CAR T-Cell therapy, works by changing the genes in a person’s T cells (a type of white blood cell) to help them find and attack cancer. It is used to treat some kinds of lymphomas, leukemias, and multiple myelomas. Early reports suggested that people treated with CAR T-cell therapy had higher rates of second cancers, such as leukemias, MDS, and T-cell lymphomas. This led the US Food and Drug Administration (FDA) to investigate and add a black-box warning (the strongest safety alert) to the therapy’s labeling. Recent research suggests that the risk of second cancer after CAR T-cell therapy may be lower and more like that seen with other cancer treatments. More study is needed.

Hormone therapies are treatments that block the hormones that cancer needs to grow. There are multiple different drugs, each working in its own way to target cancer. One of these drugs, tamoxifen, is used to treat hormone receptor-positive breast cancer and help prevent it from coming back. While the risk is low, tamoxifen can increase the chance of uterine cancer (endometrial cancer and uterine sarcoma) which can occur as a second cancer after breast cancer treatment.

Lifestyle- and environment-related risks

Certain lifestyle behaviors or habits can put a person at higher risk for some second cancers.

For some cancers, it's not clear if lifestyle may play a role in their development. For others, the cancer can be linked to things considered to be modifiable risk factors, or things that can potentially be changed to help lower cancer risk. These risk factors include:

Exposure to some carcinogens in the environment or workplace (radon, asbestos, secondhand smoke) can also put a person at higher risk for cancer.

Sometimes, development of a second cancer is linked to the same lifestyle habit as the first cancer. For example, smoking is linked to an increased risk for bladder cancer. People who have had bladder cancer have an increased risk of some other cancers linked to smoking, such as cancers of the lung, mouth, larynx, pancreas, and others.

While most cancers aren’t clearly linked to the genes we inherit from our parents, there are some gene changes or hereditary (family) cancer syndromes that can increase the risk for some second cancers. This increased risk varies depending on the type of genetic change and age of the survivor. For example, research shows that inherited gene changes play a larger role in causing a second cancer in childhood cancer survivors as compared to effects of treatments (like chemo) or lifestyle factors.

Family cancer syndromes are caused by abnormal gene changes (variants or mutations) that are often inherited from a parent. These syndromes can be linked to a higher risk for one or more kinds of cancer. Examples include:

Genetic counseling and testing with trained genetic professionals may be useful and recommended for people who have a family cancer syndrome or a higher risk for more than one kind of cancer because of family history. Talk to your cancer care team about whether genetic testing is right for your situation, as well as its cost, pros, and cons.

Reducing the risk of a second cancer

While it's not possible to predict who might get a second cancer, it’s very important that cancer survivors understand their risk for second cancers and any future health problems.

Follow-up care

Once treatment is completed, or if you're on extended treatment such as hormone therapy, you’ll continue to be closely watched by your cancer care team for a period of time. They will give you details about the follow-up care that is needed, including tests and appointments. Regular follow-up is important, as it will help monitor for signs of second cancers or cancer recurrence, manage late and long-term side effects, and manage your emotional and physical needs. 

Survivorship care plan

As part of your follow-up care, your cancer care team will likely give you a copy of your treatment summary and survivorship care plan. These documents help you organize the details of your treatment so you can plan to move forward. They can be shared with other health care professionals you see for medical care.

Your survivorship care plan explains what screenings and checkups you need to watch for post-treatment symptoms, cancer recurrence, and second cancers. It also should list which doctor will oversee the monitoring and ordering of tests.

Cancer screenings

Some survivors at increased risk for certain cancers due to their family history or genetic status may need special cancer screening. In general, survivors should otherwise continue to follow cancer screening guidelines found in the American Cancer Society Guidelines for the Early Detection of Cancer.

Healthy habits

Your survivorship care plan will also give you information on ways you can improve your overall health after treatment. Avoiding unhealthy lifestyle and environment-related risk factors can help reduce your risk of second cancers, as well as cancer recurrence. They may also help lower the risk of some other health problems like heart disease and diabetes.

For more information about follow-up care and second cancers after treatment for specific types of cancer, see each cancer type.

Questions to ask your cancer care team

  • What problems do I need to watch for?
  • What can I do to help lower my risk of a second cancer?
  • What follow-up testing do I need to do to check for second cancers?
  • What screening tests do I need and when?
  • Can you give me a copy of my treatment summary and my survivorship care plan?
  • Which doctors will oversee the monitoring and ordering of tests?

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Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).

Last Revised: October 29, 2025

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.

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