Dr Michael Murphy, University of Oxford

01 December 2011
Natural radiation exposure and childhood cancer.

It is well established that high dose radiation can induce childhood leukaemia, but the role of low dose radiation, typical of environmental exposures, is less certain. The team is building on a previous study which suggested an association between environmental radiation and childhood leukaemia. They want to confirm the results of the first study and extend their findings to cover other childhood cancers.

Award amount: £35,915  |  Date of award: December 2011

Dr Michael Murphy, Kathryn Bunch, Dr Gerald Kendall, Tim Vincent, Childhood Cancer Research Group, University of Oxford; Dr Mark Little, US National Cancer Institute; Dr Jill Meara and Jon Miles, UK Health Protection Agency; Prof Richard Wakeford, University of Manchester.

Overview
It is well established that high dose radiation can induce childhood leukaemia. However, evidence on the induction of childhood leukaemia and other childhood cancers from low dose radiation, typical of environmental exposures, is lacking.

A study of more than 27,000 childhood cancer cases, published in 2012, demonstrates an association between environmental gamma rays and childhood leukaemia. This study could be significantly improved by the use of more detailed gamma ray estimates and the inclusion of more cases and controls. The increased numbers will also allow the research team to establish whether there is a link between environmental radiation and other forms of childhood cancer.

If the findings of the first study are confirmed in this larger study, this will be of considerable importance for radiation protection including, for example, the control of medical exposures such as CT scans.

Background
Gamma rays form part of the natural background radiation that everyone is exposed to. The main source of natural gamma rays is radioactive isotopes of uranium, thorium and potassium which can be found in the soil, rocks, drinking water and even building materials.

Natural gamma ray dose rates vary across the UK, with exposures in some areas being substantially higher than in others. South Yorkshire, Cornwall, the Isles of Scilly and the Scottish Borders have the highest exposures.

Our knowledge about radiation-induced childhood cancer comes from four main sources:

i) studies of antenatal radiography have shown that irradiation in utero leads to an increased risk of leukaemia and also other cancers in childhood;
ii) studies of the survivors of the atomic bombings of Hiroshima and Nagasaki in 1945 show clearly that irradiation of children leads to a marked increase in the risk of leukaemia;
iii) studies of those exposed in childhood to radioiodine as a result of the Chernobyl accident have shown a substantial increase in the risk of thyroid cancer;
iv) studies of children exposed for medical reasons suggest an increased risk of leukaemia and solid cancers.

This information is all useful but evidence on the induction of leukaemia and other childhood cancers from radiation doses incurred at rates typical of environmental exposures is lacking.
An excellent study team with extensive experience in this area.
A study published by Dr Murphy and colleagues in 2012 has demonstrated an association between environmental gamma rays and childhood leukaemia; the team now wants to extend this study in order to explore the association further.

Project description
Dr Michael Murphy will continue to work with the team that successfully took the first analysis to completion, who together contribute unparalleled expertise in this field.
 
Based on the design of their initial study, the team will increase the number of children included in their analyses by including children born as early as 1962 and as late as 2009 (compared with 1980 to 2006 in the initial study). This should result in the inclusion of an additional 20,000 childhood cancer cases, with a similar number of controls.
The results of this study will give important input to the understanding of childhood leukaemia and other cancers.
The team will also improve estimates of gamma ray exposures. The first study used estimates of gamma ray dose rates based on the average for the County District in question; these were derived from measurements made for the National Survey of Natural Radiation. This meant that about half the case children were assigned the same gamma ray dose rate as their control; this is undesirable and reduces the power of the study. The team now has access to data that will allow them to estimate gamma ray doses more accurately; this should dramatically reduce the proportion of cases that are assigned the same gamma ray dose rate as their controls and thus substantially increase the power of the study.

What difference will this project make?
This study will allow a more detailed examination of the risks associated with low dose, natural background radiation. It will allow a better analysis of the size of the risk as well as explorations of the effect of age and gender.

This will be of considerable importance for our understanding of childhood cancer development.

Read more: Causes of childhood cancer


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