Competing interests: The BMJ has judged that there are no disqualifying financial ties to commercial companies. The authors declare the following other interests: ACM has grant funding from the Department of Veterans Affairs and has reviewed grants for the LUNGevity non-profit organization; MT has grants from the LUNGevity Foundation, American Lung Association, and National Cancer Institute and has received fees for medicolegal consulting from Quane McColl, PLLC. Further details of The BMJ policy on financial interests is here: https://www.bmj.com/sites/default/files/attachments/resources/2016/03/16-current-bmj-education-coi-form.pdf.