What Are Second Cancers?

A second cancer is a new cancer that's unrelated to any previous cancer diagnosis. It's a completely different type of cancer.

• Sometimes the new cancer is 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.
• Or, a second cancer might develop in another organ or tissue. A second cancer is different from a cancer recurrence which is when the same type of cancer that a person had before comes back.

Because it can take many years for cancers to develop, second cancers have been studied in types of cancers for which successful treatments have been around the longest. That’s why we know more about certain second cancers than others.

Who is at risk for second cancers?

It isn’t always clear what causes a second cancer or who is most at risk. Some second cancers seem to have the same or similar risk factors as a first cancer. But, the risk is known to be higher for people with certain types of cancer, who had certain types of cancer treatment, or if they have a family cancer syndrome. But for other people, the risk for a second cancer may be lower or simply isn't known.

Risk factors for a second cancer include some of the same things that are a risk for a first cancer: a healthy lifestyle and environment, using tobacco products, family history and genetics, having excess body weight (overweight or obesity), drinking too much alcohol, or the lack of good follow-up care or cancer screening after a first cancer.

When 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. And, because a person's risk for cancer generally goes up as they age, an unrelated new cancer may develop later in a cancer survivor's life.

Sometimes there are specific lifestyle recommendations and monitoring needed if a person has certain non-cancer health problems that might affect them after treatment. There might also be specific cancer screening guidelines based on a person's level of risk or if they have a family cancer syndrome. But, in general, the same cancer screening guidelines should be followed as for people who have not had cancer.