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Breast cancer survivors
Women under 45
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BRCA mutation carriers
Her2+ breast cancer
Other mutations: People with mutations in TP53, CHEK2, and PALB2
The population of breast cancer survivors in the United States is increasing. One rare but dangerous long-term effect of breast cancer treatment is an increased risk of leukemia, a type of bone marrow cancer. A recent study uncovered a potential genetic basis for this condition.
This study explores whether inherited mutations in genes that increase cancer risk are risk factors for developing leukemia after therapy. Therapy-related leukemia is a rare, late complication that develops in less than 1% of breast cancer patients who receive cytotoxic cancer therapies such as chemotherapy or radiation.
Although treatment-related leukemia is rare, the majority of people who develop the disease are breast cancer survivors. This is a rare complication, but the number of therapy-related leukemia cases will likely increase as more patients survive breast cancer. A greater understanding is needed of who is at risk for the development of therapy-related leukemia, so that better detection and prevention of this potentially lethal complication can be established. In a large study published in the Journal of Clinical Oncology in 2014, among 20,000 patients who had stage I to III breast cancers treated with various therapies, only 50 survivors developed leukemia after follow-up periods ranging from 6 months to 10 years (median follow-up was about 5 years).
Of the breast cancer survivors who developed therapy-related leukemia, about 20% had a mutation in a cancer-risk increasing gene, including mutations in BRCA1, BRCA2 and TP53.
The data from this research indicates that a inherited mutation in a gene that increases cancer risk may lead to susceptibility to therapy-related leukemia, however, more work needs to be done to fully understand this finding. It is important to remember that treatment-related leukemias are rare. If you are a BRCA1, BRCA2, TP53, CHEK2, or PALB2 mutation carrier, and you have received a cytotoxic therapy such as chemotherapy or radiation, you may wish to discuss therapy-related leukemia with your health care provider. If you are a breast cancer survivor who developed therapy-related leukemia and you are unsure if you are a carrier of a mutation that increases cancer risk, talk to your health care provider about the possibility of genetic counseling and/or genetic testing to see if you carry such a mutation.
Chemotherapy and radiation can help patients defeat their cancers, but many complications can occur during and after treatment. Breast cancer survivors are a growing population in the United States, and while they have survived their disease, they often face long-term complications and side effects. One example is developing therapy-related leukemia, a rare but potentially lethal complication of some cancer treatments.
In December 2015, Jane E. Churpek and colleagues at the University of Chicago published a study in Cancer that looked to see if inherited genetic mutations are linked to the development of therapy-related leukemia. Researchers and clinicians believe that therapy-related leukemia develops from cytotoxic therapies such as chemotherapy and radiation that cause mutations in blood cell DNA, but they do not understand why this happens to certain patients and not to others. Some breast cancer patients who are treated with surgery alone develop leukemia—this raises the possibility that some cancers that are identified as therapy-related leukemia are actually second primary cancers caused by inherited mutations in genes that are associated with increased cancer risk.
Currently, no study has looked at the possibility of increased risk for therapy-related leukemia in people who carry mutations in genes that increase cancer risk.
Are inherited cancer risk-increasing gene mutations involved in the development of therapy-related leukemia in breast cancer survivors?
The study included 88 female breast cancer survivors who received cytotoxic therapy (chemotherapy and/or radiation) after their primary breast cancer diagnosis, and later developed therapy-related leukemia. Family history and/or DNA samples for genetic testing were available for patients in the study, and genetic testing was done whenever possible.
This study is relatively small, so the researchers cannot see potential differences in therapy-related leukemia between people with mutations in different genes (for example, BRCA mutation carriers compared to TP53 mutation carriers). Because the group of patients studied was small, individuals with different types of breast cancers and different treatments were grouped together, making it harder to clearly identify groups at risk. Additionally, while this study shows that about 1 in 5 women who developed treatment-related leukemia after cytotoxic therapy for breast cancer had a mutation in a gene known to increase cancer risk, this group was not compared to mutation carriers who were treated with cytotoxic therapy but did not develop therapy-related leukemia; doing so would have provided additional information.
This study uncovers a potential link between having a mutation in a gene that increases cancer risk and susceptibility to developing therapy-related leukemia after receiving cytotoxic therapy for breast cancer. More work needs to be done to fully understand this, and to learn how therapy-related leukemia develops in these women. In the meantime, breast cancer survivors with mutations in BRCA or other genes that increase cancer risk should keep in mind that treatment-related leukemia is relatively rare, occurring in fewer than 1% of breast cancer survivors. Notably, 3 of the 47 patients with treatment-associated leukemia had inherited mutations in TP53, which is already associated with increased risk for leukemia. While this study raises the possibility of a link that should be explored further through larger studies, the results alone cannot conclude that mutation carriers are more likely to develop therapy-related leukemia than non-mutation carriers. People concerned about their risk of leukemia after treatment should discuss their risk with their health care provider.
Churpek JE, Marquez R, Neistadt B, et al. “Inherited Mutations in Cancer Susceptibility Genes are Common Among Survivors of Breast Cancer Who Develop Therapy-Related Leukemia.” Cancer. Published online first on December 7, 2015.
Wolff AC, Blackford AL, Visvanathan K, et al. “Risk of Marrow Neoplasms After Adjuvant Breast Cancer Therapy: The National Comprehensive Cancer Network Experience.” Journal of Clinical Oncology (2015), 33(4): 340-348.