Antenatal Irradiation and Childhood Cancer: Causation or Coincidence?

Abstract

A re-analysis of published data from the Oxford Childhood Cancer Survey shows that the frequency of leukaemia and of solid cancers in childhood is greater following antenatal x-radiography, not only in singleton births but also in monozygotic and dizygotic twins. The radiography rate was 10% in singletons and 55% in twins. A similar excess of leukaemia and of solid cancers in the x-rayed with such different rates of radiography is strong evidence for irradiation as the cause. The low observed frequency of malignant disease in Japanese bomb survivors exposed in utero may not be in serious conflict with this conclusion, as has been supposed.

Pre-natal irradiation and childhood malignancy: a review of British data from the Oxford Survey

“…It is true that when the risks are standardized for various epidemiological factors a small reduction in the estimates results; yet this is quite insufficient to " explain " the radiation association completely. Moreover, as pointed out by Mole (1974), the fact that the excess mortality in twins is very similar to that in singletons, despite the very different irradiation rates, militates strongly against the possibility of the x-ray excess being due to selection of pre-disposed cases for x-raying. A genuine causation would be more convincing and perhaps more in line with prior expectations if the irradiated cases exhibited more differences from the unirradiated, especially as regards age and tumour type.…”

“…However, certain categories have been excluded from the analysis, as follows: (a) cases not traced or matched with a suitable control (27%); (b) adopted children, for whom records of pre-natal irradiation are very rarely available (0.7%); (c) cases found to have benign, dubious or negative pathology (14%); (d) twins, whose pre-natal irradiation rate is very high and who are under-represented among the controls (2.2%) (see Mole, 1974;Stewart, 1973 Lymphatic M 0-6 1-8 4-2 7-4 10-6 13-3 15-5 17-4 18-9 20-2 21-3 22-5 23-6 leukaemia F 0-6 2-0 3-9 6-5 9 0 11-4 13-1 14-5 15-6 16-5 17-4 18-1 18-7 Tot 0-6 1-9 4-1 6-9 9-8 12-4 14-4 16-0 17-3 18-4 19-4 20-4 21-3 Myeloid M 0 5 1-2 1-9 2-8 3-6 4-4 5 0 5-6 6-1 6-6 7-2 7-8 8-4 leukaemia F 0 5 1-2 1 9 2-6 3-1 3-7 4-3 4-9 5-4 5-8 6-4 7 0 7-7 Tot 0 5 1-2 1-9 2-7 3-4 4-1 4-7 5-2 5-8 6-3 6-8 7-4 8-0 Allleukaemias M 2-0 4-7 9 0 14-5 19-7 24-4 28-2 31-5 34-3 36-8 39-2 41-4 43.7 Lymphomata M 0-4 0-8 1-4 2-2 3 0 3-9 4.9 5.7 6-7 7-6 8-4 9-3 10-4…”

“…Although most of the scientific world has accepted the evidence for the carcinogenicity of low-level irradiation (Mole, 1974), there is still a lingering controversy, which is based mainly on the incompatibility of the risk-per-rad estimates obtained from the Oxford Survey on the one hand and from the ABCC data on Japanese bomb survivors on the other. The main argument currently hinges on the comparability of the x-rayed and non-x-rayed mothers, examined below.…”

Carcinogenic risks of prenatal ionizing radiation

“…Twin studies have been used to eliminate some of the confounding factors [87e89]. Although the reports of Mole [89] and Harvey et al [87] were positive, the Rodvall study [88] was not statistically significant.…”

“…Boice and Miller [78] have concluded that the more recent data have reduced the discrepancy between these two extreme viewpoints. Based on the reports of Muirhead and Kneale [82] and Mole [89] they believe that 'The risk estimate associated with intrauterine radiation is not substantially greater than that seen following childhood irradiation. ' Doll and Wakeford [90] expressed their opinion about the carcinogenic effect of intrauterine radiation and concluded that 'Irradiation of the fetus in utero increases the risk of childhood cancer, and increases the risk from exposures of the order of 10 mGy, and that in these circumstances the excess risk is w6% per Gy.…”