Standard errors of non-standardised and age-standardised relative survival of cancer patients

Relative survival estimates cancer survival in the absence of other causes of death. Previous work has shown that standard errors of non-standardised relative survival may be substantially overestimated by the conventionally used method. However, evidence was restricted to non-standardised relative survival estimates using Hakulinen's method. Here, we provide a more comprehensive evaluation of the accuracy of standard errors including age-standardised survival and estimation by the Ederer II method.

Five- and ten-year non-standardised and age-standardised relative survival was estimated for patients diagnosed with 25 common forms of cancer in Finland in 1989-1993, using data from the nationwide Finnish Cancer Registry. Standard errors of mutually comparable non-standardised and age-standardised relative survival were computed by the conventionally used method and compared with bootstrap standard errors.

When using Hakulinen's method, standard errors of non-standardised relative survival were overestimated by up to 28%. In contrast, standard errors of age-standardised relative survival were accurately estimated. When using the Ederer II method, deviations of the standard errors of non-standardised and age-standardised relative survival were generally small to negligible.

In most cases, overestimations of standard errors are effectively overcome by age standardisation and by using Ederer II rather than Hakulinen's method.