Acknowledgements
We thank Laufey Tryggvadóttir from the Icelandic Cancer Registry, Hólmfríður Gunnarsdóttir from the Faculty of Medicine, University of Iceland and Pär Sparén from the Department of Epidemiology and Biostatistics of the Karolinska Institute in Stockholm for their contributions to the NOCCA project and their contributions to this letter.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.