Article publication date:
Lopes et al.
This systematic review and meta‑analysis reviewed current evidence on the risk of developing central nervous system (CNS) tumours in relation to the ionising radiation (IR) exposure at low-to-moderate doses received during adulthood or adolescence. A total of 18 studies were included in the systematic review, whilst data from 12 studies were used in the meta-analysis in order to estimate the pooled excess relative risk (ERRpooled). The IR exposures considered were occupational (e.g., nuclear workers and uranium miners, military using nuclear materials, medical workers, flight attendants, Chernobyl clean-up workers) and environmental (atomic bomb exposure/background). The study found that ERRpooled at 0.1 Gray was − 0.01; 95% CI: − 0.05, 0.04). The review and meta-analysis, which mostly reviewed the studies involving IR doses of 0.1 Gray, concluded that there is no evidence of a dose–response association between IR exposure and risk of CNS tumours. The authors also acknowledged the limitations in the studies including the lack of histological information on CNS tumours, large uncertainties in IR dose assessment, and the over-representation of men in the different occupational cohorts.
Ionizing radiation exposure during adulthood and risk of developing central nervous system tumors: systematic review and meta-analysis
Commentary by ARPANSA:
This study showed that low-to-moderate doses of IR exposure in adulthood is not associated with the risk of CNS tumours. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) states at low levels (less than 0.1 Gray) IR exposure, the possible increased risk of cancer is uncertain (UNSCEAR, 2017). These findings contrast with those provided by other studies; Little et al., 2022 suggest higher risk of cancer following low to high doses (less than 0.1 Gray) of IR exposures in childhood. In particular, a large population-based Australian study has also indicated that medical radiation exposure (e.g., CT scans) during childhood and adolescence could increase cancer incidence rates in populations for all cancers, including brain tumours (Mathews et al 2013). The differences in the overall conclusion of these studies could be partly attributed to children’s higher radiosensitivity compared to that of adult humans, and study methods adopted in the different included studies. Future studies need to consider accurate IR dosimetry and collection of information on potential confounders – this would help enhance our knowledge on the effects of low-to-moderate doses of IR in adulthood/adolescence on the risk of CNS tumours.
ARPANSA publishes a series of evidence-based documents to guide Australian radiation protection principles and practices for radiation workers and the general public. For example,
The Code for Radiation Protection in Planned Exposure Situations (2020) established a framework in Australia for the protection of occupationally exposed persons, the public and the environment in planned IR exposure situations. This guide applies the three main principles of radiation protection: i) justification (that any activity involving IR exposure should do more good than harm), ii) optimisation (that actual IR exposure, likelihood of exposures and number of exposed persons should be as low as reasonably achievable taking into account economic and societal factors), and dose limits (levels of radiation dose that must not, under normal circumstances, be exceeded). ARPANSA will continue to update the latest science on human radiation protection, including cancer risk associated with IR exposure, in order to protect Australian population.