A critical review of methods for assessing cancer survival disparities in indigenous population

An increasing cancer burden among indigenous populations has led to a growing literature about survival disparities between indigenous and nonindigenous persons. We aim to describe and appraise methods used to measure cancer survival in indigenous persons in the United States, Canada, Australia, and New Zealand.

We searched Medline, Web of Science, and EMBASE for articles published between 1990 and 2015 that estimated survival in populations indigenous to one of these four countries. We gathered information about data sources, analytical methods, and the extent to which threats to validity were discussed.

The search retrieved 83 articles. The most common approach to survival analysis was cause-specific survival (n = 49). Thirty-eight articles measured all-cause survival and 11 measured excess mortality attributable to cancer (relative survival). Three sources of information bias common to all studies (ethnic misclassification, incomplete case ascertainment, and incomplete death ascertainment) were acknowledged in a minority of articles.

The methodological considerations we present here are shared with studies of cancer survival across other subpopulations. We urge future researchers on this and related topics to clearly describe their data sources, to justify analytic choices, and to fully discuss the potential impact of those choices on the results and interpretation.