1. Cancer Epidemiology and Health Services Research Group; Centre for Public Health; Queen's University Belfast; Belfast UK
2. Academic Primary Care; Institute of Applied Health Sciences; University of Aberdeen; Aberdeen UK
3. Section of Epidemiology and Population Sciences; Department of Medicine; Baylor College of Medicine; Houston TX USA
4. Centre for Cancer Research and Cell Biology; Queen's University Belfast; Belfast UK
5. Belfast Health and Social Care Trust; Belfast UK
6. Medical Statistics Team; Institute of Applied Health Sciences; University of Aberdeen; Aberdeen UK