Background The imminent publication of a randomised controlled trial from the USA that suggests CT screening reduces mortality from lung cancer by more than 20%, may potentially lead to one of the most important developments in lung cancer care. However, there remain important questions about the applicability of the results to the UK and the clinical effectiveness of this intervention, including its feasibility and cost-effectiveness.

Objective To describe the remaining questions that need to be answered by further research and to comment on the use of CT screening in the UK outside a clinical trial.

Methods The detailed design process of the UKLS protocol and international discussions were used to identify the research questions that remain to be answered and to inform those who may choose to consider offering CT screening, before these questions are answered.

Results A series of research imperatives have been identified and we advise that CT screening should be part of the ongoing clinical trial in the UK, currently in the pilot phase (UKLS). UKLS is randomising 4,000 individuals for the pilot and a total of 32,000 for the main study.

Conclusion There remain unresolved issues with respect to CT screening for lung cancer. These include its feasibility, psychosocial and cost-effectiveness in the UK, harmonisation of CT acquisition techniques, management of suspicious screening findings, the choice of screening frequency and the selection of an appropriate risk group for the intervention. UKLS is aimed at resolving these issues.