Health Library: ABCDEFGHIJKLMNOPQRSTUVWXYZ

Cancer Caused by Chemotherapy or Radiation

Fortunately, the likelihood of chemotherapy or radiation treatment causing a second cancer is rare. And in most cases, the potential benefits of the treatment far outweigh the risks. Nevertheless, cancer can occur in some instances, so it’s important to be aware of the potential risks involved before undergoing these cancer treatments.

Cancer caused by chemotherapy

Chemotherapy drugs are effective in the treatment of many cancers, but these powerful drugs also pose the risk of causing leukemia in some patients. In fact, the risk of developing leukemia is higher when taking chemotherapy drugs than with radiation therapy. Also, the risk grows as the length of treatment increases or the dose of the drugs gets higher.

The types of chemotherapy drugs that appear to pose the greatest risk of causing leukemia are known as alkylating agents, and several drugs fall into this class. With these drugs, the risk for a second cancer seems to develop slowly over time. Studies have shown that the risk begins to rise about two years after treatment, is highest about five to 10 years after treatment, and then gradually decreases.

In recent years, the chemotherapy drug cisplatin, the class of chemotherapy drugs known as topoisomerase II inhibitors, and chemotherapy drugs called anthracyclines have also been linked to leukemia.

These drugs are most likely to cause a type of leukemia known as acute myelogenous leukemia. In about 5 to 10 percent of leukemia cases linked to chemotherapy, the type that results is acute lymphocytic leukemia.

Cancer caused by radiation therapy

Radiation therapy can also increase the risk of developing leukemia in some people. The types of leukemia linked to radiation therapy include acute myelogenous leukemia, chronic myelogenous leukemia, and acute lymphoblastic leukemia. These cases typically develop a few years after radiation exposure with the peak of risk being about five to nine years after exposure.

Some other cancer risks are tied to radiation therapy, as well. Solid tumors can develop at or near the site of the radiation exposure even 10 or more years after the radiation therapy. These risks seem to be greatest in certain areas of the body, such as the breast and the thyroid. In some of these cases, your age at the time of radiation treatment plays a role. For example, younger breast cancer patients are more likely to develop a second cancer from radiation therapy than older breast cancer patients.

The bottom line on second cancers

The reality is that all cancer patients run the risk of developing a second cancer. Some are related to treatment options, but many are not. And in most cases, the potential benefits of treatment greatly outweigh the risks.

The best thing you can do to protect yourself from developing a second cancer is to work closely with your doctor and make sure that you have extensive and thorough follow-up appointments after your treatments. You can also help yourself by avoiding other risk factors for cancer, such as smoking.