Health Risks from Exposure to Low Levels of Ionizing Radiation BEIR VII Phase 2 (2006) / Chapter Skim
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7 Medical Radiation Studies
7 Medical Radiation Studies
Pages 155-188
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From page 155... ...
Population-based cancer reg In addition to studies of cancer survivors, long-term studistries in many countries have been used to identify these ies of patients who received radiation therapy for benign patients and to facilitate patient enrollment, thus allowing conditions such as enlarged tonsils and tinea capitis have investigators to determine the risks of a second primary can also provided important information about radiation-induced cer after treatment with radiation for a primary cancer (Boice cancer risk (UNSCEAR 2000b)
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From page 156... ...
; Diagnostic Radiation Exposures (2) individual quantitative estimates of radiation dose to the organ of interest were available for the study subjects; (3)
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From page 157... ...
From these data, UNSCEAR (2000b) within this cohort, allowed the reconstruction of individual doses to specific organs and the estimation of site-specific 1ERR is the rate of disease in an exposed population divided by the rate cancer risks (Boice and others 1987, 1988, 1989)
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From page 158... ...
. A cohort study of second cancer risk following radiation In 1995, Boivin and collaborators published results of a therapy for cancer of the uterine cervix was also carried out joint Canada-U.S.
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From page 159... ...
Little if between radiation exposure and lung cancer resulting from any increased risk was seen for patients treated after age 30. that radiation exposure, only doses received more than Most recently, Dores and colleagues (2002)
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From page 160... ...
; a significant dose-response ischemic heart disease, the OR was 1.13 (95% CI 1.03, 1.25)
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From page 161... ...
MEDICAL RADIATION STUDIES 161 1970 and 1993 and registered in cancer registries in Iowa, life expectancy of children with cancer and increased the Connecticut, New Jersey, Canada (Ontario) , Denmark, Fin- chance of development of second cancers.
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From page 162... ...
many survivors of these cancers live long enough to develop In a joint analysis of data from childhood cancer survivor a second, treatment-related malignancy, these studies have cohorts from France, Britain, and Nordic countries, a nested provided valuable information on the magnitude of risk case-control study of melanoma was carried out. Radio following radiation exposure.
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From page 163... ...
MEDICAL RADIATION STUDIES 163 used in the treatment of benign conditions were generally diotherapy compared to those who did not. Overall, a 50% not as high as those used to treat malignant disease so that increase in the risk of all cancers combined was observed.
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From page 164... ...
No estimate of risk per unit dose was pre- (based on 741 deaths) , decreasing significantly to 0.11 Gy1 sented.
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From page 165... ...
A linear- There was no increased cancer risk among those treated with exponential model (in which the exponential term allows for 131I and no indication of a relation with 131I activity delivcell sterilization in heavily exposed parts of the bone mar- ered. Nonsignificant increased risks were seen for cancers in row)
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From page 166... ...
tumors among women was an tic ulcer have provided valuable information for the quantiincreased risk seen (RR 1.89, based on 17 cases) ; the RR fication of radiation risk estimates for cancers of the lung, was higher among those who received total 131I activities of breast, and stomach and for leukemia.
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From page 167... ...
MEDICAL RADIATION STUDIES 167 in the above cohort has been published (Sadetzki and others lowed by mail questionnaire to evaluate the incidence of 2002) , but there were no risk estimates.
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From page 168... ...
Doses to 11 organs were Two Swedish cohort studies have been performed of pa- calculated on the basis of 226Ra activity, location of the hetients treated for skin hemangioma in infancy. In the first mangioma, and estimated absorbed dose rate in these organs study (Lundell and others 1994)
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From page 169... ...
The slope of the doseEAR, however, increased with time since exposure. Neither response relationship appeared to reach a maximum 25 age at exposure, dose rate, nor ovarian dose appeared to have 29 years after exposure, but response continued to be elan effect on the ERR.
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From page 170... ...
Breast cancer risk increased 2.1 Gy (range 018.4) in Nova Scotia and 0.79 Gy (range 0 significantly with increasing radiation dose.
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From page 171... ...
retion to prior exposure to diagnostic X-rays, one of tumors of ported on cancer risk in this population over the same pethe parotid gland and the other of chronic myeloid and mono riod. For each patient, information on delivered 131I activity, cytic leukemia.
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From page 172... ...
tween radiation dose and risk of breast cancer, such as the Estimates from these studies are reviewed in detail, and com severity of disease, which may affect reproductive history pared with risk estimates derived from other medical expo and hence breast cancer risk. sure studies, in the section "Evaluation of Risk for Specific Cancer Sites." Studies of diagnostic 131I exposures reviewed did not pro- CT scans vide estimates of risk per unit dose.
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From page 173... ...
A small excess of thyroid supported by the increase in RR with increasing number of cancer risk was seen -- based on very small numbers -- and X-ray examinations conducted in the third trimester of preg- no risk estimate is provided. nancy and the significant decline in RR with year of birth, paralleling the decline in fetal doses that occurred over the EVALUATION OF RISK FOR SPECIFIC CANCER SITES same period (UNSCEAR 1972)
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From page 174... ...
They do, chapter was used to identify the studies that are informative however, illustrate the range and significance of estimates for radiation risk estimation and have provided estimates of obtained and provide some indication of the influence of the risk per gray in a comparable fashion (either as ERR or as study-specific factors involved.
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From page 175... ...
MEDICAL RADIATION STUDIES 175 has been implicated as a lung carcinogen (UNSCEAR radiation for peptic ulcer. Although risk estimates from these 2000b)
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From page 176... ...
is available in which study, the mean age at first exposure was 10.1 years, while exposure occurred at very young ages and protracted low in the other studies, the majority of subjects were adults at dose-rate exposures were received. Risk estimates from that the time of radiation exposure.
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From page 177... ...
MEDICAL RADIATION STUDIES 177 TABLE 7-3 Risk Estimates for Cancer Incidence and Mortality from Studies of Radiation Exposure: Female Breast Cancer Average ERR EAR/ Radiation Dose Dose Controls/ per 104 PY/ Reference Study Type (Gy) Range Cases Population Gy LB UB Gy LB UB Comments Incidence Boice and Cervix External 0.3 953 1,806 0.20 <0.2, 0.3 Overall others (1988)
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From page 178... ...
178 BEIR VII FIGURE 7-2 Distributions of study-specific estimates of ERR and EAR for breast cancer according to level of average dose to the breast.
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From page 180... ...
The ERR/Gy was cancer risk and evaluate the role of modifying factors. The greater among Japanese atomic bomb survivors; this differanalyses included studies of the following populations: Japa- ence may be partly attributed to the lower background rates nese atomic bomb survivors (Thompson and others 1994)
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From page 181... ...
The ERR appeared to decline over time TABLE 7-4 Risk Estimates for Cancer Incidence and Mortality from Studies of Radiation Exposure: Thyroid Cancer Average EAR/ Radiation Dose Dose Controls/ ERR/ 104 PY/ Reference Study Type (Gy) Range Cases Population Gy 95% CI Gy LB UB Comments Incidence Ron and Tinea capitis External 0.09 98 10,834 30.0 13.0 others (1989)
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From page 182... ...
182 BEIR VII FIGURE 7-4 Distribution of study-specific estimates of ERR/Gy for thyroid cancer according to level of average thyroid dose. NOTE: The estimate from populations exposed to131 I is excluded.
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From page 183... ...
Estimates of risk from average doses ranging from 0.1 to 2 Gy, are relatively close, 226Ra alone or in combination with external radiation are in the range 1.9 to 5 Gy1, and are statistically compatible. TABLE 7-5 Risk Estimates for Cancer Incidence and Mortality from Studies of Radiation Exposure: Leukemia Excluding CLL Average ERR EAR/ Radiation Dose Dose Controls/ per 104 PY/ Reference Study Type (Gy)
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From page 184... ...
184 BEIR VII - FIGURE 7-5 Distribution of study-specific estimates of ERR/Gy for leukemia according to level of average dose to the active bone marrow.
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From page 185... ...
Both animal and human studies have identified intimal thickening, lipid deposition, and adventitial fibroses of the TABLE 7-6 Risk Estimates for Cancer Incidence and Mortality from Studies of Radiation Exposure: Stomach Cancer Average EAR/ Radiation Dose Dose Controls/ ERR/ 104 PY/ Reference Study Type (Gy) Range Cases Population Gy 95% CI Gy LB UB Comments Incidence Boice and Cervix External 2 0.53.5 348 658 0.54 (0.05, 1.5)
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From page 186... ...
low doses (on the order of 5 Gy) and for high doses (in the Excess heart disease mortality has been observed among region of 40 Gy)
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From page 187... ...
DISCUSSION Many studies lack the sample size and high-quality dosim Since the publication of BEIR V (NRC 1990) , new infor- etry that are necessary for precise estimation of risk as a mation concerning health effects of radiation exposures has function of dose, a point that is illustrated by the large confibecome available from epidemiologic studies of populations dence intervals for many of the risk estimates shown in exposed to medical uses of ionizing radiation.
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From page 188... ...
The magnitude mation about thyroid cancer risks. For subjects exposed be- of the radiation risk and the shape of the dose-response curve low the age of 15, a linear dose-response was seen, with a for these outcomes, if an effect exists, are uncertain.
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