Exploration of the possible effect on survival of lead-time associated with implementation of cancer patient pathways among symptomatic first-time cancer patients in Denmark.

•Improvements in cancer 1-year survival is often criticised for being an effect of lead-time bias.•Implementation of fast tracks has induced lead time by faster diagnosis.•This study is the first to use real observed data to explore the impact of lead time from fast tracks.•Lead time can explain 13% of one-year survival improvement seen across the time of fast track implementation.•The survival improvement across time of fast track implementation seems mainly to reflect a true survival improvement.