Risk of childhood cancer from fetal irradiation.

Abstract

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.

Insights into the cellular origin and etiology of the infant pro-B acute lymphoblastic leukemia with MLL-AF4 rearrangement

“…This unambiguous conclusion is derived from data on Japanese atomic bomb survivors from 1945 who were acutely exposed to up to 4200 mSv 43 and, at a much lower dose level (B10 mSv), from historical data on diagnostic exposure of the fetus from X-ray pelvimetry during pregnancy. 44 Unfortunately, most of these environmental exposures lack a biological rationale or consistent epidemiological evidence. Although there might not be a single or exclusive cause, an abnormal immune response to common infection(s) has emerged as a plausible etiological mechanism for childhood leukemias.…”

New germline mutations in the hypervariable minisatellite CEB1 in the parents of children with leukaemia

“…However, epidemiological studies have failed, with one exception, to identify decisively these carcinogens. This exception involves exposure of the unborn child to X-rays in utero, which is associated with a B50% increased risk of childhood leukaemia (Stewart et al, 1956;Stewart and Kneale, 1968;Stewart and Kneale, 1970;Bithell and Stewart, 1975;Doll and Wakeford, 1997;Wakeford and Little, 2003).…”

Imaging strategies to reduce the risk of radiation in CT studies, including selective substitution with MRI

“…A follow-up review published in 1987 (12) considered that a causal explanation is supported by evidence indicating an appropriate dose-response relationship, as well as by animal experiments, and concluded that radiation doses on the order of 10 mGy received by the fetus in utero produce a consequent increase in the risk of childhood cancer (12). They reported that the excess absolute risk coefficient is approximately 6% per gray of radiation exposure (12). Historical data from the early days of diagnostic x-ray imaging indicate that malignancies arose from excessive exposure to the x-rays.…”