Leukemia refers to a group of cancers that arise from the white blood cell-forming tissues of bone marrow. Leukemia develops when the genetic material of this tissue undergoes changes that lead to uncontrolled replication of the cell type involved. The four major categories of leukemia are acute and chronic lymphocytic leukemia, and acute and chronic myeloid leukemia. Although it remains unclear why any given person develops leukemia, certain identifiable factors may contribute to its evolution.
Radiation Exposure
Radiation is an invisible form of energy, similar to other energy forms such as magnetic and electrical energy. Energy travels through space and objects, its presence apparent only when it causes a noticeable effect. For example, the electrical energy in a car battery is unseen but declares its presence when the car starts in response to turning the ignition. Low-level radiation occurs naturally in the environment and causes no known harm. However, exposure to high-level industrial, medicinal and weapons-related radiation can damage the genetic material of the human body and may contribute to the development of leukemia. The National Cancer Institute reports that people exposed to high-energy radiation from nuclear weapons and medical radiation therapy have an increased risk for the development of various forms of leukemia.
Benzene and Smoking
Benzene is a common chemical used in many types of industries, from gasoline and oil processing to pharmaceutical production. Cigarette smoke also contains substantial amounts of benzene. According to the National Toxicology Program's "Report on Carcinogens," benzene is a potential cancer-causing chemical. The report notes that a significant association exists between benzene exposure and an increased risk for acute myeloid leukemia.
Benzene exposure occurs primarily through the inhalation of vapors from gasoline, motor vehicle exhaust and occupational uses. Cigarette smoke also remains a significant source of benzene exposure. The "Report on Carcinogens" says cigarette smoke accounts for approximately 50 percent of the total exposure to benzene nationwide. Thus, smokers have an increased risk for the development of leukemia because of high-level benzene exposure.
Cancer Chemotherapy
Certain types of cancer chemotherapy drugs may contribute to the development of acute myeloid leukemia several years after treatment. The Abramson Cancer Center of the University of Pennsylvania reports that the chemotherapy drugs most commonly associated with the late development of leukemia include cytoxan, ifosfamide, mephalan, etoposide, mitoxantrone, cisplatin, daunorubicin and doxorubicin. Overall, leukemias that develop after previous cancer chemotherapy respond poorly to additional chemotherapeutic treatment.
Human T-cell Leukemia Virus Type I
Human T-cell leukemia virus Type I, or HTLV-I, has a strong association with adult T-cell leukemia-lymphoma. This white blood cell cancer occurs most commonly in Japan, certain regions in Africa, the Caribbean islands and parts of South America. Although approximately 90 percent of people with adult T-cell leukemia-lymphoma have HTLV-I infection, most people with this viral infection do not develop leukemia, note Drs. Kensei Tobinai and Toshiki Watanabe in the medical reference text "Clinical Oncology." This important finding reinforces what doctors and scientists have long theorized--that a constellation of factors, rather than a single cause, leads to the development of leukemia.
References
- National Cancer Institute: What You Need to Know About Leukemia, Risk Factors
- National Toxicology Program: Report on Carcinogens, Eleventh Edition--Benzene
- Abramson Cancer Center of the University of Pennsylvania OncoLink: Acute Myeloid Leukemia
- "Clinical Oncology, Third Edition"; Martin D. Abeloff, M.D., et al., Editors; 2004
- American Cancer Society: What are the Risk Factors for Acute Myeloid Leukemia?
