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Background: International cancer survival comparisons use cancer registration data to report cancer survival, which informs the development of cancer policy and practice. Studies like the International Cancer Benchmarking Partnership (ICBP) have a duty to understand how registration differences impact on survival prior to drawing conclusions., Methods: Key informants reported differences in registration practice for capturing incidence date, death certificate case handling and registration of multiple primary tumours. Sensitivity analyses estimated their impact on one-year survival using baseline and supplementary cancer registration data from England and Sweden., Results: Variations in registration practice accounted for up to a 7.3 percentage point difference between unadjusted (estimates from previous ICBP survival data) and adjusted (estimates recalculated accounting for registration differences) one-year survival, depending on tumour site and jurisdiction. One-year survival estimates for four jurisdictions were affected by adjustment: New South Wales, Norway, Ontario, Sweden. Sweden and Ontario's survival reduced after adjustment, yet they remained the jurisdictions with the highest survival for breast and ovarian cancer respectively. Sweden had the highest unadjusted lung cancer survival of 43.6% which was adjusted to 39.0% leaving Victoria and Manitoba with the highest estimate at 42.7%. For colorectal cancer, Victoria's highest survival of 85.1% remained unchanged after adjustment., Conclusion: Population-based cancer survival comparisons can be subject to registration biases that may impact the reported 'survival gap' between populations. Efforts should be made to apply consistent registration practices internationally. In the meantime, survival comparison studies should provide acknowledgement of or adjustment for the registration biases that may affect their conclusions., (Copyright © 2018. Published by Elsevier Ltd.)

BACKGROUND Countries with a similar expenditure on healthcare within Europe exhibit differences in lung cancer survival. Survival in lung cancer was studied in 2001-2004 in England, Norway and Sweden. METHODS Nationwide cancer registries in England, Norway and Sweden were used to identify 250 828 patients with lung cancer from England, 18 386 from Norway and 24 886 from Sweden diagnosed between 1996 and 2004, after exclusion of patients registered through death certificate only or with missing, zero or negative survival times. 5-Year relative survival was calculated by application of the period approach. The excess mortality between the countries was compared using a Poisson regression model. RESULTS In all subcategories of age, sex and follow-up period, the 5-year survival was lower in England than in Norway and Sweden. The age-standardised survival estimates were 6.5%, 9.3% and 11.3% for men and 8.4%, 13.5% and 15.9% for women in the respective countries in 2001-2004. The difference in excess risk of dying between the countries was predominantly confined to the first year of follow-up. The relative excess risk ratio during the first 3 months of follow-up comparing England with Norway 2001-2004 varied between 1.23 and 1.46, depending on sex and age, and between 1.56 and 1.91 comparing England with Sweden. CONCLUSION Access to healthcare and population awareness are likely to be major reasons for the differences, but it cannot be excluded that diagnostic and therapeutic activity play a role. Future improvements in lung cancer management may be seen early in follow-up.