The Arctic Aeromedical Laboratory's Thyroid Function Study A Radiological Risk and Ethical Analysis (1996) / Chapter Skim
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2 Health Effect of I131 Administration in Humans
2 Health Effect of I131 Administration in Humans
Pages 26-42
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From page 26... ...
However, serious shortcomings lunit its use in modern nuclear medicine. The major drawback of }~3} iS the relatively high radiation dose received by Me thyroid.
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Dr. RodahI, the principal physician and investigator on the AAL project, had at the time of the experiments completed the required training, which involved 30 hours of participation in an instruction program and experience diagnosing and treating 49 cases using radioactive materials.
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28 The ALL Thyroid Function Study Box 2~..~.
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3. Thyroid cancer risk from external irradiation has a significant age dependency.
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4. Current epidemiological evidence on thyroid cancer induced by external irradiation is consistent with a linear dose-response curve.
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~ identifies several major studies that provide risk estimates of radiation-induced thyroid cancer (Ron et al., 19951. All the studies cited involved external irradiation of subjects as a result of atomic bomb irradiation or radiation therapy for the treatment of various benign diseases or cancer (other than thyroid cancer)
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From page 32... ...
Combined, the studies discussed above include about 120,000 people, nearly 700 thyroid cancers, and about 3 million person-years of follow-up (Ron et al., 19951. Except for the atomic bomb survivor and the cervical cancer patient studies, which include adult subjects, risk estimates provided in Table 2.!
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From page 33... ...
The average activity noted for each population group was derived from the AAL reports; the dose conversion factors (which convert the amount of radioactivity administered into a thyroid radiation dose) were based on calculations provided by Oak Ridge Institute for Science and Education based on current computer models of internal radiation dosunetry of the thyroid gland for elm.
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_ . ED The CAL Thyroid Function Study ^ cat '= ~ cat ~ cat _ ct 0 .= ~ ~ c r ~ Ct O ~ -= O Cal en X ~ O Sit ~ .= 7 ~ ~ i_ Cal A: o Cal O ~ Cal X ~ A: o .
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From page 36... ...
iodine metabolism in white military personnel before and after a four-week cold exposure in the field. Inspection of Table 2.3 reveals a wide range of thyroid doses and thyroid cancer risk estimates in the population groups participating in the AAL studies.
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To put these risks into perspective, it is useful to consider the natural incidence of thyroid cancer in the population and Me lifetime risk of thyroid cancer in the absence of radiation exposure. Thyroid cancer is a rare form of cancer (American Cancer Society, Inc., 19951.
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Radiationinduced thyroid cancers caused by the AAL study would not be expected in the Alaska Native or white military personnel experunental subjects. The Committee is unaware of any reports of thyroid cancer in the irradiated population.
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From page 39... ...
The possibility that thyroid cancer could result from radiation exposure was first documented in 1950, but those cases resulted from large doses used for therapeutic purposes. In 1955, Sunpson and colleagues conducted one of the earliest studies linking thyroid cancer in children with external radiation treatment for thymic enlargement (Simpson et al., 19554.
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From page 40... ...
What emerged from the studies of the Japanese survivors and patients who had received radiation for the treatment of various medical conditions was the belief that any dose of radiation may be harmful and that the major health effect of exposure was cancer. As a consequence, occupational exposure standards were reduced to 5 roentgens per year in 1956.
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~ :::~R I~E..OF:~.3 ~ my, ~ ,,;; , ~ ~ , :~ I .
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From page 42... ...
of a radioactively labeled drug should be the smallest radiation dose Mat can be administered without jeopardizing the benefits to be obtained from the study. The limit for the thyroid gland is 5 red as a single dose and 15 red as a cumulative dose from a number of studies conducted within one year.
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