Can Cancer Treatments cause Cancer? Understand your risk of acquiring a secondary cancer.

It is not a recurrence, and it is not a metastasis (the spread of cancer from one part of the body to another). A secondary cancer, or second primary cancer, is a new cancer that develops in a person who has had cancer before.

“It’s a different type of cancer,” explains Kamal Patel, MD, Medical Director of Radiation Oncology at Cancer Treatment Centers of America® (CTCA) in Zion, Illinois. “A secondary cancer develops at least two months after primary diagnosis,” he says. “It’s a separate tumor that’s very different from recurrence or metastasis.”

Pamela Crilley, DO, Chief of Medical Oncology at CTCA® in Philadelphia, Pennsylvania, explains that secondary cancers can be caused by treatment for the first cancer, such as radiation therapy or certain chemotherapy drugs. She adds, however, that treatment is not always the cause. “It is also possible for a patient to have a second cancer that is unrelated either to the primary cancer or to the initial treatment,” she says.

Fortunately, due to advances in treatments, secondary cancers are relatively rare today. As a patient or survivor, however, it is still important to be aware of the risk and the value of follow-up and screenings. “Early detection is important to improve outcomes,” explains Dr. Crilley.

The Link Between Treatment and Secondary Cancers
Two big culprits in secondary cancers are radiation and chemotherapy, and they carry different risks. “Radiation is more likely to result in solid tumors that occur 10 to 20 years or more after treatment,” says Dr. Patel. He explains that chemotherapy is more likely to cause nonsolid tumors (such as cancers of the blood), which tend to occur in the first 10 years after treatment.

According to Dr. Crilley, solid tumors occur more frequently as secondary cancers than do blood cancers. “An example of a solid tumor arising from treatment would be breast cancer in a patient who had been treated years earlier for a Hodgkin’s lymphoma with radiation therapy to the chest,” she explains. Lung cancer, she says, is another example and can occur 10 or 15 years or even longer after initial exposure to treatment.

“The biggest concern with secondary cancers is for pediatric patients,” says Dr. Patel. Children exposed to radiation or chemotherapy may have full life expectancies, giving them more opportunity to develop another cancer.

Reducing Risk
Though secondary cancers remain an important consideration for survivors, perhaps the most significant message about risk is that advances in treatment are allowing doctors to limit this threat. The emphasis, says Dr. Patel, is on treating the current cancer while limiting long-term side effects.

Dr. Patel admits, however, that safety cannot be entirely guaranteed when it comes to the affect of cancer treatment. For example, “There is no safe dose of radiation,” he says, “but we’re aware of the risk and try to limit exposure.”

Newer technology that limits radiation exposure includes proton radiation therapy. This approach uses streams of protons (tiny particles with a positive charge) to kill tumor cells. Because radiation is targeted at cancer cells, exposure to surrounding healthy tissues is reduced. The goal is a lower risk of long-term complications, including secondary cancers.

Long-term risks related to chemotherapy have also been reduced as research related to treatment has advanced. “Selection of chemotherapy agents to eliminate or minimize exposure to alkylating agents [shown to increase the risk of secondary cancers] will decrease the risk of long-term second malignancies, such as certain types of leukemia, lymphoma or blood disorders,” Dr. Crilley explains.

As a patient, says Dr. Crilley, you can play a role in making informed decisions about your treatment and the potential long-term risk of a secondary cancer. She encourages patients to ask questions and become well informed. “In-depth discussions with your oncology providers, including your radiation and medical oncologists, will provide insight to help you understand any potential risks, short or long term,” she says.

The considerations you and your doctor will take into account include personal factors and treatment options, says Dr. Crilley. “Your age at the time of the initial treatment of the primary cancer may influence selection of which treatment would be least likely to cause long-term adverse effects,” she explains.

Screening and Prevention
Once you have made an informed decision to move forward with a treatment that carries a risk of secondary cancer, you can take important steps to reduce your risk or detect a secondary cancer early, if one develops.

“Effective screening is available for patients at risk for a secondary cancer,” says Dr. Crilley. “For example,” she explains, “in women at risk for breast cancer after treatment with radiation for Hodgkin’s lymphoma, a yearly breast MRI [magnetic resonance imaging scan] may detect an early secondary cancer.” She adds that, similarly, patients at risk for lung cancer after radiation can be screened with a CT [computed tomography] scan. In any case, secondary cancers that are found early can be treated early, which can improve outcomes.

You can also take proactive steps of your own to reduce your risk. “Lifestyle can make a difference,” says Dr. Patel. He recommends avoiding smoking (which can make treatment less effective and increase the risk of side effects, including secondary cancers), avoiding alcohol in excess or altogether, engaging in regular physical activity and eating a healthy diet.

Remain Vigilant
Awareness and close follow-up remain important measures for reducing your risk of secondary cancers. Though the risk of secondary cancers with current treatment is not great, in some cases it remains a long-term, or ongoing, complication. “As a survivor, you’ll want to continue close follow-up with your oncology care team,” says Dr. Patel.

Ultimately, survivors should be encouraged by the fact that advances in treatment to limit long-term complications mean the risk of a secondary cancer is likely very low. And remember, your oncologist’s goal is to choose treatment that effectively treats current cancer with minimal long-term risks.


  • written by Mia James from CTCA