The last thing anyone wants to hear after their breast cancer has gone into remission is that they need another round of cancer treatments. Unfortunately, this can happen when breast cancer comes back.

It can also happen when a secondary cancer, such as leukemia, develops.

Secondary cancers are cancers that develop as a result of cancer treatments or other risk factors after the initial cancer has gone into remission. A secondary cancer can develop months or even years after cancer treatments are complete.

People who’ve been treated for breast cancer can develop leukemia as a secondary cancer.

Keep reading to learn more about the risk of developing leukemia after breast cancer, what causes it to develop, how it’s treated, and more.

It’s estimated that around 0.5% of people treated for breast cancer go on to develop secondary leukemia. This is different from a recurrence of breast cancer after remission.

Leukemia after breast cancer treatment is a new and different cancer. It’s not breast cancer returning.

Leukemia can be either acute or chronic. Acute leukemias grow and spread quickly, while chronic leukemias spread slowly.

In most cases, the type of leukemia that develops after breast cancer treatment is acute. Acute myeloid leukemia (AML) is the most common type of leukemia to develop as a secondary cancer after breast cancer treatment.

Cancer treatments, such as radiation and chemotherapy, affect both cancer cells and healthy cells. It’s known that exposure to radiation can increase the risk for certain cancers.

Additionally, researchers believe that treatment for breast cancer damages the DNA inside your bone marrow. The cells inside your bone marrow are responsible for making blood cells. Damage to bone marrow DNA can affect blood cell production. In rare cases, this can lead to leukemia, because leukemia is a blood cancer.

A 2019 study has indicated that it’s possible that these DNA mutations might already exist in some people. This research theorizes that chemotherapy and radiation treatments activate pre-existing mutations, and could explain why secondary leukemia only happens to a small number of people who’ve had breast cancer treatments.

If further studies confirm these findings, it could allow doctors to identify people who are at risk for secondary leukemia before breast cancer treatments even begin.

Other cancers following breast cancer

The most common cancer people get following breast cancer is another breast cancer. Having breast cancer once increases your risk for additional breast cancer tumors.

Other types of cancer that sometimes occur after breast cancer treatment include:

Leukemia can develop months or years after breast cancer treatment. It’s a good idea to keep all follow-up appointments, and to report any new symptoms to your doctor.

Some leukemia symptoms can seem minor or like the symptoms of less serious conditions at first, but reporting them quickly can make a difference in treatment options and outcomes. If you’ve had any leukemia symptoms for more than a week or two, let your doctor know.

Leukemia symptoms include:

Your treatment for leukemia will depend on several factors, including your overall health, how far the leukemia has spread, and how well you responded to chemotherapy and radiation during breast cancer treatment.

Remember that the leukemia isn’t a recurrence of the breast cancer. It’s a new cancer that will need to be treated separately.

Treatment options include:

  • Chemotherapy: Chemotherapy is the primary treatment for all forms of leukemia and is used to kill cancer cells.
  • Radiation therapy: Radiation therapy uses energy to kill cancer cells.
  • Targeted therapy: Targeted therapy uses specialized medications to find, block, and kill cancer cells.
  • Immunotherapy: Immunotherapy teaches your immune system to find and destroy cancer cells.
  • Bone marrow transplants: A bone marrow transplant, sometimes called a stem cell transplant, is a procedure that replaces your unhealthy bone marrow cells with cancer-free bone marrow cells. The healthy cells can come either from your own body or from the body of a donor. You can read more about bone marrow transplants here.

The outlook for leukemia depends on a number of factors including:

  • how far the leukemia has spread at diagnosis
  • your overall health
  • how well you respond to treatment
  • your age

According to the National Cancer Institute, between 2012 and 2018 the 5-year survival rate for all types of leukemia was 65.7 percent.

Over the past several decades, survival rates have consistently trended upwards. It’s likely this trend will continue as new and more effective treatment options are developed.

A small but significant percentage of people who are treated for breast cancer eventually develop secondary leukemia as a result of treatment.

Researchers are still doing studies to determine what causes this increased risk for leukemia and what can be done to reduce that risk. Currently, it’s believed that a combination of the known risks of radiation along with the possible pre-existing genetic factors, could lead to secondary leukemia.

It’s a good idea to pay attention to any signs and symptoms you experience following breast cancer treatment and report them to your doctor right away. Early diagnosis can increase your treatment options and improve your outlook.