Risk of childhood cancer from fetal irradiation.
Tóm tắt
The association between the low dose of ionizing radiation received by the fetus in utero from diagnostic radiography, particularly in the last trimester of pregnancy, and the subsequent risk of cancer in childhood provides direct evidence against the existence of a threshold dose below which no excess risk arises, and has led to changes in medical practice. Initially reported in 1956, a consistent association has been found in many case-control studies in different countries. The excess relative risk obtained from combining the results of these studies has high statistical significance and suggests that, in the past, a radiographic examination of the abdomen of a pregnant woman produced a proportional increase in risk of about 40%. A corresponding causal relationship is not universally accepted and this interpretation has been challenged on four grounds. On review, the evidence against bias and confounding as alternative explanations for the association is strong. Scrutiny of the objections to causality suggests that they are not, or may not be, valid. A causal explanation is supported by evidence indicating an appropriate dose-response relationship and by animal experiments. It is concluded that radiation doses of the order of 10 mGy received by the fetus in utero produce a consequent increase in the risk of childhood cancer. The excess absolute risk coefficient at this level of exposure is approximately 6% per gray, although the exact value of this risk coefficient remains uncertain.
Từ khóa
Tài liệu tham khảo
MacMahon B, 1962, J Natl Cancer Inst, 28, 1173
Hewitt D, 1966, Monthly Bull Ministry of Health and Public Health Laboratory Service, 25, 80
Bithell JF., 1989, Low dose radiation: biological bases of risk assessment.
Bithell JF., 1993, Neue Bewertung des Strahlenriskos: Niedrigdosis-Strahlung und Gesundheit.
Monson RR, 1984, Radiation carcinogenesis: epidemiology and biological significance.
United Nations Scientific Committee on the Effects of Atomic Radiation., 1972, Ionizing radiation: levels and effects. 1972 Report to the General Assembly, with annexes. Vol II. Effects
Morin M, 1991, CR Acad Sci Paris, 312, 629
Benjamin SA, 1986, J Natl Cancer Inst, 77, 563
United Nations Scientific Committee on The Effects of Atomic Radiation., 1994, Sources and effects of ionizing radiation. 1994 Report to the General Assembly, with scientific annexes
Greaves MF, 1993, Leukemia, 7, 349
Muirhead CR, 1993, Chilton: National Radiological Protection Board, 15
National Research Council., 1990, Health effects of exposure to low levels of ionizing radiation. BEIR V
Shimizu Y, Kato H, Schull WJ. Studies of the mortality of A-bomb survivors. Report 9. Mortality, 1950-1985: Part 2. Cancer mortality based on the recently revised doses (DS86).Radiat Res1990; 121:120-41.
United Nations Scientific Committee on the Effects of Atomic Radiation., 1986, Genetic and somatic effects of ionizing radiation. 1986 Report to the General Assembly, with annexes
Shore RE, 1985, J Natl Cancer Inst, 74, 1177
Yoshimoto Y, Kato H, Schull WJ. Risk of cancer among in utero children exposed to A-bomb radiation, 1950-84. Technical Report RERF TR 4-88.Hiroshima: Radiation Effects Research Foundation, 1988.
Shimizu Y, 1950, Mortality, 85, 3
Magnin P., 1962, Presse Med, 70, 1199
Draper GJ, 1982, Childhood cancer in Britain: incidence, survival and mortality. Studies on Medical and Population Subjects No. 37
Mills SD, 1958, Minnesota Med, 41, 339
Nokkentved K., 1968, Effect of diagnostic radiation upon the human foetus. Follow-up study of 152 children exposed to irradiation during the first 4 months of foetal life due to X-ray examination of the maternal abdomen
Breslow NE, 1987, Statistical methods in cancer research, 82