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Mounting evidence of cancer risk from low dose radiation in childhood, or in the uterus.

Cancer risks among studies of medical diagnostic radiation exposure in early life without quantitative estimates of dose

Science Direct, 1 August 2022, Mark P. Little ^a1, Richard Wakeford ^b1, Simon D. Bouffler ^c, Kossi Abalo ^d, Michael Hauptmann ^e, Nobuyuki Hamada ^f, Gerald M. Kendall ^g

Highlights

• •There is mounting evidence of cancer risk from low dose radiation in childhood.
• •A review was conducted of cancer after exposure in utero/childhood of studies without individual radiation dose estimates.
• •There were excess cancer risks associated with radiation exposure in utero.
• •There were excess cancer risks associated with radiation exposure in childhood, but also substantial variability in effect.
• •These data suggest excess risk following diagnostic radiation exposure in utero, but not after postnatal exposure.

Abstract

Background

There is accumulating evidence of excess risk of cancer in various populations exposed at acute doses below several tens of mSv or doses received over a protracted period. There is also evidence that relative risks are generally higher after radiation exposures in utero or in childhood.

Methods and findings

We reviewed and summarised evidence from 89 studies of cancer following medical diagnostic exposure in utero or in childhood, in which no direct estimates of radiation dose are available. In all of the populations studied exposure was to sparsely ionizing radiation (X-rays). Several of the early studies of in utero exposure exhibit modest but statistically significant excess risks of several types of childhood cancer. There is a highly significant (p < 0.0005) negative trend of odds ratio with calendar period of study, so that more recent studies tend to exhibit reduced excess risk. There is no significant inter-study heterogeneity (p > 0.3). In relation to postnatal exposure there are significant excess risks of leukaemia, brain and solid cancers, with indications of variations in risk by cancer type (p = 0.07) and type of exposure (p = 0.02), with fluoroscopy and computed tomography scans associated with the highest excess risk. However, there is highly significant inter-study heterogeneity (p < 0.01) for all cancer endpoints and all but one type of exposure, although no significant risk trend with calendar period of study.

Conclusions

Overall, this large body of data relating to medical diagnostic radiation exposure in utero provides support for an associated excess risk of childhood cancer. However, the pronounced heterogeneity in studies of postnatal diagnostic exposure, the implied uncertainty as to the meaning of summary measures, and the distinct possibilities of bias, substantially reduce the strength of the evidence from the associations we observe between radiation imaging in childhood and the subsequent risk of cancer being causally related to radiation exposure……………………..

“In the present paper we review studies of early life medical diagnostic exposures, both 61 antenatal and postnatal, in which quantitative radiation dose estimates are lacking, though general indications of the magnitude of the doses are likely to be implicit. The present study complements  a parallel and contemporary review that evaluated studies in which quantitative estimates of radiation risk with respect to doses are available (Little et al., 2022b).”…………….. https://www.sciencedirect.com/science/article/abs/pii/S0048969722018162

July 19, 2024 - Posted by Christina Macpherson | radiation