Chemotherapy affects normal, healthy cells as well as breast cancer cells. This is why chemotherapy can cause hair loss, anemia, and diarrhea. In rare cases, exposing normal cells to cancer treatments such as chemotherapy and radiation therapy can cause a new, different type of cancer to develop many years after treatment.
Radiation therapy uses a special kind of high-energy beam to damage cancer cells. Over time, radiation damages cells that are in the path of its beam -- normal cells as well as cancer cells. But cancer cells are more affected by radiation than normal cells because they’re less organized. Normal cells are better able to repair themselves and survive the treatment.
While the risk of developing leukemia after radiation therapy or chemotherapy to treat early-stage breast cancer is VERY small, a large study suggests that this risk is twice as high as has been reported.
The research was published online on Dec. 22, 2014 by the Journal of Clinical Oncology. Read the abstract of "Risk of Marrow Neoplasms After Adjuvant Breast Cancer Therapy: The National Comprehensive Cancer Network Experience."
Both radiation therapy and chemotherapy can be given after breast cancer surgery to lower the risk of the cancer coming back (recurrence). Treatments given after surgery are called adjuvant treatments.
"Bone marrow neoplasms" are the general medical term for all types of leukemia, which is cancer of the bone marrow.
In the study, researchers from the Johns Hopkins Kimmel Cancer Center looked at information from more than 20,000 women who had been treated for early-stage breast cancer at eight U.S. cancer centers between 1998 and 2007. The women’s recurrence rates and any additional cancer diagnoses were recorded in a database kept by the National Comprehensive Cancer Network (NCCN). The NCCN is an alliance of the world's leading cancer centers. These NCCN centers collaborate on research, guidelines, and education to improve the care of people diagnosed with cancer.
Most of women in the study had treatment after surgery:
- about 25% had only radiation therapy
- about 16% had only chemotherapy
- about 46% had chemotherapy and radiation therapy
- about 13% had neither chemotherapy nor radiation therapy
Of the women in the study, 50 developed some type of leukemia in the 10 years after radiation therapy, chemotherapy, or both treatments. This means the women had about a 0.5% risk of developing leukemia.
In earlier studies, which included only a few hundred women, the risk of developing leukemia after radiation and/or chemotherapy for early-stage breast cancer was 0.25%.
It’s very important to know that the rate of leukemia after breast cancer treatment is very small. Still, many doctors think that women are only at risk in the first few years after treatment. This study suggests that the risk continues through 10 years after treatment and is higher than what was thought.
Because of treatments they’ve received, many breast cancer survivors have a higher risk of developing other diseases as they age, including other cancers, high blood pressure, heart disease, and osteoporosis. To make sure breast cancer survivors are regularly screened for these and other diseases they may be at higher risk for, experts have developed the idea of survivorship care planning. If you’ve been treated for early-stage breast cancer, it’s very important that you regularly see a doctor (or doctors) who are familiar with your medical history and understand your special risks.
If you’re finished with treatment and your oncologist hasn’t talked to you about a survivorship care plan, it’s a good idea to bring it up at your next appointment. Here are some questions you may want to ask your oncologist:
- Can I get a survivorship care plan in writing that explains all the medical issues I need to consider and tells me which screening tests I need and when I should have them?
- Which doctor should I see for each medical issue?
- If your oncologist recommends that you see a specialist -- a cardiologist for example -- and you’ve never seen one before, you may want to ask for a referral to a specific doctor.
- If there is anything in your survivorship care plan that you don’t understand, ask your doctor or nurse to explain it.
It’s also a good idea to talk to your primary care doctor about your survivorship care plan and ask which parts of it she or he will be responsible for.