A comparison of relative and cause‐specific survival by cancer site, age and time since diagnosis

Relative survival (RS) estimates are widely used by cancer registries, mainly because they do not rely on the well‐documented deficiencies of cause of death information. The aim of our study was to compare 5‐year cause‐specific survival (CSS) estimates and 5‐year RS estimates for different cancer sites by age and time since diagnosis, and discuss possible reasons for observed differences. Using data from the Cancer Registry of Norway, we identified 200,008 patients diagnosed with cancer at one of the 48 sites included in this analysis during the period 1996–2005, and followed them up until the end of 2010. CSS estimates were calculated (i) considering cause of death to be the cancer that was originally diagnosed and (ii) considering the cause of death to be a cancer within the same organ system. For most cancer sites the difference between CSS and RS estimates was small (