Estimating net survival using a life-table approach

Cancer registries are often interested in estimating net survival, the probability of survival if the cancer under study is the only possible cause of death. In 2011, Pohar Perme et al. proposed a new estimator of net survival based on inverse-probability weighting. They demonstrated that existing estimators of net survival based on relative survival were biased, whereas the new estimator was unbiased. However, the Pohar–Perme estimator was developed for continuous survival times, yet cancer registries often only have discrete survival times (for example, survival time in completed months or completed years). We propose an approach to estimation when survival times are discrete and life table estimation is applied. A new Stata command, stnet, allows a life-table estimation of net survival, adapting the Pohar–Perme approach to life-table estimation. Age-standardized survival estimates are available. In addition to the traditional cohort and complete approach, estimates can also be made using a period or hybrid approach. With examples, we describe the main feature of the new command and illustrate some comparison of the results produced by our life-table approach and the time-continuous approach developed on R software. The new command is available for download from the SSC-Archive.