Risk of Leukemia from Radiation

Exposure to ionizing radiation is a risk factor for leukemia.

Only four years after the tsunami and nuclear meltdown in Japan, the first case of radiation-related leukemia was reported.

Radiation has both short- and long-term effects. Provoking the development of a cancer is considered a long-term effect. Leukemia -- and especially acute myelogenous leukemia, or AML -- is among the most likely malignancies to develop following exposure to high levels of radiation, and cases can emerge in as few as four years.

How Do We Know Radiation Causes Leukemia?

The link between radiation exposure and leukemia has been observed in history. Leukemia was diagnosed disproportionately in the earliest radiologists, in Japanese bomb survivors and in British children who had been irradiated in utero.

A link between radiation and leukemia was first suspected in 1911, after a number of occupationally exposed individuals developed leukemia. Wilhelm Roentgen had discovered x-rays in the late 1800s, just before the turn of the century, and by 1911 cases of leukemia were already starting to be linked to radiation exposure.

How Long After Radiation Does Leukemia Emerge?

Not every one who is exposed to radiation develops leukemia, and individual differences can also factor into a person's risk. However when leukemia develops following radiation exposure, in contrast to many other cancers, it tends to follow the exposure by years rather than by decades.

After the exposure to ionizing radiation, there is a latent period during which there are no signs of cancer. The latent period for leukemia is believed to be about 4 to 7 years, with the number of cases steadily increasing until about 7 to 10 years after exposure.

How Much Radiation is Safe?

There is no known “threshold dose.”  That is, when it comes to future cancer development, there is no level that serves as a boundary between 'no risk' and 'risk.' Instead, the risk of leukemia is believed to increase in step with the radiation exposure.

In cases of radiation therapy delivered to cancer patients and diagnostic imaging studies such as CT scans, it is not that the exposure to radiation is completely without risk, but for any one person the risk of radiation-induced cancer is much smaller than the natural risk of cancer. The small increase in radiation-associated cancer risk for an individual can become a public health concern only if large numbers of the population undergo increased numbers of CT screening procedures of uncertain benefit. In general, when a CT scan is obtained the benefits and risks have been weighed carefully and the benefits are believed to substantially outweigh the risks.

Does the Kind of Radiation Exposure Matter?

High levels of whole-body radiation such as in nuclear accidents are believed to carry the most risk. Radiation therapy does carry some risk, however. According to the American Cancer Society, most kinds of leukemia can be caused by past radiation exposure, and the risk of leukemia after radiation treatment depends on factors including how much of the bone marrow was exposed to radiation, how much radiation reached the bone marrow, and the way it was delivered -- how much radiation was in each dose, how frequently the dose were given, and how long it took to give the dose.

People exposed to ionizing radiation have an increased risk of developing acute lymphoblastic leukemia, acute myelogenous leukemia, and chronic myelogenous leukemia.

First Fukushima Worker Develops Leukemia

After the tsunami of 2011, international attention was focused on the nuclear meltdowns affecting the Fukushima Daiichi nuclear power plant in Japan. According to the Washington Post, more than 44,000 workers were deployed to take the facility safely offline. The clean up job involved millions of gallons of radioactive water. In 2015, four years later, Japan’s ministry of health, labor and welfare confirmed a worker at Fukushima was diagnosed with exposure-related leukemia. The 41-year-old man was diagnosed with acute myelogenous leukemia, or AML.

Sources

Radiation Protection and Dosimetry: An Introduction to Health Physics; Michael G. Stabin. 2007.

Principles and Practice of Radiation Therapy; Charles M. Washington, Dennis T. Leaver. 2015.

Hall E, Giaccia A. Radiobiology for the radiologist. Ed 7. Philadelphia: Lippincott Williams & Wilkins; 2012.

Davis A, Viera A, Mead M. Leukemia: an overview for primary care. Am Fam Physician. 2014 May 1;89(9):731-8.

Bhatia S, Robison LL. Epidemiology of leukemia and lymphoma. Curr Opin Hematol. 1999;6(4):201–204.

Yoshinaga S, Mabuchi K, Sigurdson AJ, Doody MM, Ron E. Cancer risks among radiologists and radiologic technologists: review of epidemiologic studies. Radiology. 2004;233(2):313–321.

American Cancer Society. Second Cancers in Adults. http://www.cancer.org/acs/groups/cid/documents/webcontent/002043-pdf.pdf Accessed October 2015.

Washington Post. http://www.washingtonpost.com/news/morning-mix/wp/2015/10/20/for-the-first-time-fukushima-recovery-worker-diagnosed-with-cancer-report-says/ Accessed October 2015.

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