Background radiation and childhood leukemia: A nationwide register‐based case‐control study

Abstract

High doses of ionizing radiation are an established cause of childhood leukemia. However, substantial uncertainty remains about the effect of low doses of radiation, including background radiation and potential differences between genetic subgroups of leukemia have rarely been explored. We investigated the effect of the background gamma radiation on childhood leukemia using a nationwide register-based case-control study. For each of the 1,093 cases, three age- and gender matched controls were selected (N = 3,279). Conditional logistic regression analyses were adjusted for confounding by Down syndrome, birth weight (large for gestational age), and maternal smoking. Complete residential histories and previously collected survey data of the background gamma radiation in Finland were used to assess the exposure of the study subjects to indoor and outdoor gamma radiation. Overall, background gamma radiation showed a non-significant association with the OR of childhood leukemia (OR 1.01, 95% CI 0.97, 1.05 for 10 nSv/h increase in average equivalent dose rate to red bone marrow). In subgroup analyses, age group 2-<7 years displayed a larger effect (OR 1.27, 95% CI 1.01, 1.60 for 1 mSv increase in equivalent cumulative dose to red bone marrow). Suggestive difference in OR by genetic subtype was found. Our results provide further support to the notion that low doses of ionizing radiation increase the risk for childhood leukemia, particularly at age 2-<7 years. Our findings suggest a larger effect of radiation on leukemia with high hyperpdiploidy than other subgroups, but this result requires further confirmation.

NOD Scid Gamma Mice Are Permissive to Allogeneic HSC Transplantation without Prior Conditioning

“…Similarly, positive associations between protracted low dose radiation exposure and leukemia have been reported for the Techa River Cohort [8] and radiation-monitored workers [9]. Interestingly, a similar association has been postulated for human cohorts born in areas with high natural background radiation [10,11,12]. The profound changes to the HSC niche following myeloablative conditioning of murine recipients greatly compromise our ability to study low dose radiation exposure and the effects on the HSCs and their contribution towards long-term hematopoiesis in a biologically relevant setting.…”

Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)

“…The key characteristics of the material have been presented previously. 10 Briefly, all cases of childhood leukemia (M9800–M9948 in ICD-O-3) diagnosed in Finland during 1990–2011 (n=1,100) before the age of 15 years were identified from the Finnish Cancer Registry (Figure 1). Three controls were individually matched, by sex and year of birth, for each case from the Population Register Center.…”

“…9 A higher risk has also been suggested for older parental age, delivery by Cesarean section, and paternal smoking. 10–13 However, daycare attendance, allergic diseases, maternal folic acid supplementation before birth, and early immune stimulation have been suggested to reduce the risk of leukemia. 14–17 …”

Predicting residential radon concentrations in Finland: Model development, validation, and application to childhood leukemia

“…Using statistics, we modelled indoor radon concentration in a given dwelling using measurements from the nationwide database and internally validated its performance and robustness. Then we applied the model to examine potential association between residential radon and childhood leukemia using data from a nationwide childhood leukemia case-control study (48).…”