What causes second cancer?

It’s hard to know exactly what causes second cancers. There are many known risk factors that can increase your cancer risk. So a second cancer can be caused by whatever caused the first cancer. A second cancer can also be caused by the treatment used to treat the first cancer. Here are some of the things linked to second cancers:

Radiation therapy for your first cancer

Radiation treatment kills cancer cells. But it can also damage nearby normal cells. Over time, this can lead to another cancer. This means radiation to a certain part of the body can raise the risk for a new cancer growing in that same area. It may cause tumors that don’t show up for many, many years after treatment.

For instance, radiation to the chest to treat breast cancer can damage lung cells, too. This may lead to lung cancer in the future. If a lot of your bone marrow (the thick liquid inside your bones) is exposed to radiation, it may cause leukemia (a blood cancer). Radiation for prostate cancer may lead to bladder or rectal cancer. For the most part, the more radiation you've had, the higher the risk for a second cancer in the area that was treated.

Chemotherapy for your first cancer

Certain chemotherapy (chemo) medicines have been linked to a higher risk for second cancer. And some are linked to getting the blood cancer called leukemia later in life. The risk is higher if you had high doses of chemo. Or got it for a long time. Make sure to ask your healthcare team if the chemo you had can raise your risk for leukemia or any other types of cancer in the future. 

Targeted therapy for your first cancer

Because these medicines are newer, researchers are still learning about their connection to second cancers. Some targeted therapy medicines that treat melanoma may increase a person's risk for squamous cell carcinoma of the skin.

Other factors

There are many possible causes of cancer. The most important risk factor for most types of cancer is age. This means surviving cancer once means you will grow older and be at a higher cancer risk. Certain lifestyle factors are also linked to some types of cancer. These include:

• Using tobacco and exposure to secondhand smoke

• Drinking alcohol

• Eating a poor diet

• Being overweight

• Being exposed a lot to UV rays from the sun

Other risk factors linked to cancer are:

• Gene changes that are passed down in families

• Infection with certain viruses, such as human papillomavirus and HIV

• Jobs with exposure to harmful substances

What is my risk for a second cancer?

People who have had cancer are often at higher risk for other types of cancer. In fact, about 1 out of 6 people with cancer had a different kind of cancer in the past.

The risk of a second cancer is higher if you had cancer treatment as a child or young adult.

Risk varies depending on the type of cancer you had and the types of treatments you had. It also depends on your family’s history of cancer and your overall health and lifestyle.

Your healthcare providers can tell you more about your personal risk for certain kinds of second cancers. They can also tell you what you can do to help decrease your risk and what you should watch for.

Can I lower my risk for second cancer?

There's no sure way you can prevent a second cancer. But you can take steps to help lower your risk:

• Eat a healthy diet with plenty of vegetables, fruits, and whole grains. Limit red and processed meats, as well as sugary drinks.

• Get exercise every day.

• Get to or stay at a healthy weight. Ask your healthcare provider for help.

• Don’t use any form of tobacco. Ask your provider for help quitting.

• Stay away from alcohol. If you choose to drink, limit alcohol to 1 drink a day if you are a woman and 2 per day if you are a man.

A key step to lower your risk for a second cancer is getting routine cancer screenings. Screening tests look for cancer when it's small and hasn't spread. They can help find some kinds of cancer before you have symptoms. Most cancer survivors should follow general screening guidelines. Talk with your healthcare provider about the screening schedule that's best for you.

Checking for second cancer

Keep your follow-up appointments with your healthcare team. Your providers will ask you how you're feeling. They'll also ask what, if any, changes or symptoms you have. Get regular cancer screening tests as advised by your healthcare provider.

Also, be sure to tell your healthcare team if you have new symptoms that don’t go away, such as:

• Pain

• Trouble breathing

• Lumps or swelling

• Unplanned weight loss

• Easy or unusual bleeding or bruising

• Fevers

• Blood in your urine or stool

• Abnormal vaginal bleeding or discharge

• Nausea, vomiting, or diarrhea

• A cough that doesn’t get better

• Tiredness that doesn’t get better with rest

• Skin changes

• Sores that don’t heal

Keep in mind that these symptoms may be, and are most likely, caused by other things. You may have an infection or other problems that can be easily treated. Still, only your healthcare provider can tell for sure that these changes aren't caused by a second cancer.

Working with your healthcare team

Talk with your healthcare team about what kinds of second cancer you may be at risk for. They can help you understand what to watch for and what you can do to help lower your risk. They can also make sure you get the recommended cancer screening tests.

The most important thing about watching for and coping with second cancer is working with your healthcare team. Your team can give you information and support. They can help you stay healthy.