Leukemia after Breast Cancer Treatment: What are the Causes?

Months or years after getting treated for breast cancer, some patients develop secondary leukemia, or therapy-related leukemia.

In some cases, patients may be at higher risk because of genetic mutations that are already present in their blood cells. However, breast cancer treatment itself can cause secondary leukemia.

Exposure to radiation may increase secondary leukemia risk. Researchers also believe that breast cancer treatment might damage the DNA in the cells in your bone marrow, which are responsible for making blood cells. This in turn may cause leukemia, a blood cancer.

Usually, secondary leukemia after breast cancer happens due to a specific class of chemotherapy drugs called anthracyclines, which are commonly used to treat breast cancer, said Saranya Chumsri, MD, a hematologist-oncologist at the Mayo Clinic in Jacksonville, Florida.

Secondary leukemia is very rare. Only about 0.5% of people treated for breast cancer develop leukemia as a result of their treatment. Because other cancers don’t commonly use anthracycline as treatment, breast cancer accounts for most cases – about 70% – of secondary acute leukemia, Dr. Chumsri said.

Despite the rarity of secondary leukemia, doctors now closely weigh the risks and benefits of using anthracyclines, Dr. Chumsri said. “There are a lot of efforts to stay away from anthracyclines, but in certain subtypes of breast cancer, particularly triple-negative breast cancer, which is an aggressive type, we still kind of need it,” she said. “It’s not like we have a lot of other alternatives.”

For this reason, prior exposure to anthracycline is a risk factor.

Having breast cancer once raises your risk of having it again. Secondary metastatic breast cancer can go to any of the following organs:

• Salivary glands

• Esophagus

• Stomach

• Colon

• Uterine

• Ovarian

• Thyroid

• Soft tissues

• Skin (melanoma)

Depending on the cancer, this increased risk may stem from exposure to radiation or certain chemotherapy drugs. Tamoxifen, a hormone therapy used to treat estrogen receptor-positive breast cancer, can slightly raise the risk of secondary uterine cancer.

Higher risk can also be due to certain genetic mutations—for example, mutations in the BRCA genes raise the risk of both breast and ovarian cancers.

Leukemia signs and symptoms include:

• Fever or chills

• Persistent fatigue or weakness

• Frequent or severe infections

• Unexplained weight loss

• Swollen lymph nodes

• Enlarged liver or spleen

• Easy bleeding or bruising

• Recurrent nosebleeds

• Tiny red spots on your skin

• Excessive sweating, especially at night

• Bone pain or tenderness

• Shortness of breath

• Pale skin

See your doctor if you start to experience any of these after you’ve been treated for breast cancer, especially if you’ve received anthracyclines.

The prognosis for secondary leukemia after breast cancer is usually poor, said Dr. Chumsri, in part because most women who develop secondary leukemia tend to be those with aggressive breast cancer. “These patients also normally have multiple mutations in the leukemia itself,” she said. “Even with treatment, secondary leukemia is very difficult to treat.”

Some factors that can affect your outlook include:

• Cancer subtype

• Age

• Smoking status

• Alcohol use and diet

• Overall health

• Whether your leukemia is acute (fast-spreading) or chronic (slow-spreading) – most cases of therapy-related leukemia are acute

• Family history

• Genetic mutations linked to cancer

Treatments for secondary leukemia are generally the same as for leukemia in general. These depend on a few different factors, including your leukemia subtype and your overall health. Possible treatments include chemotherapy, radiation, targeted therapy, immunotherapy, or bone marrow transplant.

Treatment for therapy-related leukemia after breast cancer is usually palliative, said Dr. Chumsri, meaning the goal is to make the patient as comfortable as possible at their end of life. This can affect your treatment choices since some therapies can be very taxing, involving disruptive hospital stays, or they are aggressive and can make you feel very sick.

Some other approaches that focus on relieving your symptoms may include:

• Acupuncture

• Exercise

• Massage

• Meditation

• Relaxation activities such as yoga or tai chi

Detecting breast cancer right away is the key to avoiding secondary cancers like leukemia, Dr. Chumsri said. “That’s why screening is so important” However, early-stage breast cancer may still need anthracycline but ultimately the risk of secondary leukemia is very low.