Radiation Dose Effects in Relation to Obstetric X-Rays and Childhood Cancers

271

127

Summary.-This paper reviews data relating to obstetric radiography from the Oxford Survey of Childhood Cancers, i.e. for deaths in Britain from 1953 to 1967.Some 8513 cases were traced and used in the analyses, together with an equal number of matched controls. The relative risk estimate (1.47 overall) does not vary significantly between different tumour groups, for different ages at death, nor between sexes. Other epidemiological factors-sibship position, maternal age, social class, region of residence and maternal morbidity-are analysed and show varying degrees of association, but not sufficient to " explain " the observed risk in terms of a selection effect. The dependence of the risk on the number of films exposed is highly significant and adequately described by a linear relationship. The timing of and reason for the exposure are also examined. Analysis of the risk by year of birth shows a pattern of steadily declining risk for both solid and haematopoietic tumours; this may be partly attributable to lower radiation doses per film exposed but is also due to the smaller numbers of films used. A consequence may well be that the risk-always of small clinical significance-would become virtually undetectable in future investigations.

Section: (3) Epidemiological Factorsmentioning

confidence: 83%

Section: (3) Epidemiological Factorsmentioning

confidence: 83%

Section: (3) Epidemiological Factorsmentioning

confidence: 99%

See 1 more Smart Citation

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

Bithell¹,

Stewart²

1975

271

127

“…Given these assumptions Jablon and Kato (1970) showed that there were far fewer tumours after antenatal irradiation in bomb survivors than would be expected from the estimates of risk per rad of diagnostic x-rays provided by Stewart and Kneale (1970a). Jablon and Kato's (1970) argument was as follows: The whole population of Japanese bomb survivors irradiated in utero included 1 cancer death between 0 and 10 years of age (Table II (l from Table I of Jablon an(l Kato (1970) ancd On the other hand, the basic assumptions underlying these comparisons may be in error.…”

Section: Japanese Bomb Survivors Irradiated In Uteromentioning

confidence: 99%

Antenatal Irradiation and Childhood Cancer: Causation or Coincidence?

Mole¹

1974

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.

“…It is ctustomary to wait until the foetus is at least 6 months old before resorting to obstetric radiography (Stewart et al, 1958;Stewart and Kneale, 1970a); and leukaemias with intervals of less than 3 years between birth and diagnosis are not as common among the cases caused by obstetric radiography as they are among the non-radiogenic cases (Stewart and Hewitt, 1965;Stewart and Kneale, 1970b). It is therefore possible that the third trimester is a relatively late date for initiating a childhood leukaemia, and that most of the cases in this age range are genuine embryomata.…”

mentioning

confidence: 99%

Cancer as a Cause of Abortions and Stillbirths: the Effect of these Early Deaths on the Recognition of Radiogenic Leukaemias

Stewart¹

1973

Summary.-Data from the Oxford Survey have shown that childhood cancers are causes of in utero deaths which affect leukaemias more than solid tumours and difficult deliveries more than easy ones. As a result of these biases singletons give the impression of being more leukaemia-sensitive than twins. This is a false impression which affects other situations and makes it more difficult to detect the leukaemogenic effects of obstetric radiography in a prospective survey than in a case-history survey, and essential to look for these effects beyond the period affected by the in utero deaths.