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

Background: Implementation of standardised cancer patient pathways (CPPs) has provided faster diagnosis of cancer. Cancer survival has improved during the same time period. Concern has been raised that the faster diagnosis may have introduced lead-time bias by elongating the period from diagnosis to death. Aim: We aimed to analyse the possible effect of lead time on survival due to expedited cancer diagnosis after the implementation of national CPPs among incident cancer patients diagnosed through Danish primary care. Material and methods: We used actual observed differences in diagnostic intervals to estimate the lead-time effect. We used data from sub-cohorts from the Danish Cancer in Primary Care (CaP) cohort of first-time cancer patients: before and after CPP implementation. To calculate differences in absolute survival, we estimated the survival function after advancing the date of diagnosis in the before cohort to an earlier point in time and hereby adjusting for lead time for nine cancer types and all combined by using Kaplan-Meier analysis. Results: Advancing the date of diagnosis implied that the absolute one-year survival increased from 68.5% to 69.4%. This accounted for 13% of the observed differences in absolute one-year survival from before to after CPPs. Conclusion: The lead time caused by shorter diagnostic intervals after implementation of Cancer Patient Pathways seems to explain less than 15% of the observed changes in the one-year survival estimates for cancer patients in Denmark. (C) 2017 Elsevier Ltd. All rights reserved.