Monitoring temporal trends in cancer survival; choosing appropriate standards when accounting for age and other-cause mortality variation over time

Background: Along with incidence and mortality, temporal trends of cancer survival are a crucial part of cancer surveillance and control. The most common reported statistic is net survival, usually age standardized to an external reference population. However, net survival has an awkward interpretation, which has led to confusion and misunderstanding. Methods: We describe the use of reference adjusted all-cause survival and the crude probability of death as an alternative to net survival for the analysis of temporal trends in cancer survival. Reference adjusted measures aim to enable fair comparisons by incorporating additional reference expected mortality rates into the estimation process. The different approaches are illustrated using data on 95,285 women diagnosed with breast cancer in Norway 1986-2021. Results: We compare different age distributions for age standardization and describe how using a recent calendar period for both the reference expected mortality rates and age distribution for standardization leads to simple interpretation. Conclusions: Reference adjusted measures for monitoring temporal trends in cancer survival can lead to improved understanding and is of more relevance to patients and policy makers who live and make decisions in the real-world. Using the most recent calendar period for both the age standard and the reference expected mortality rates leads to simple and useful interpretation of the measures. Impact: Increasing the use of reference adjusted measures in the analysis of population-based cancer studies will enhance understanding of cancer survival trends. The freely available software increases the likelihood of uptake.