Unstaged cancer: Long-term decline in incidence by site and by demographic and socioeconomic characteristics.

PURPOSE: The study of trends in stage at diagnosis contributes to understand disease burden and the effects of cancer control activities. However, a proportion of cancers reported to registries have insufficient information to assign stage. The limited research addressing unstaged cancers has noted racial and socioeconomic disparities. Long-term incidence trends for unstaged cancers have not been described. We examined long-term trends in diagnosis of unstaged cancers in the U.S. Surveillance, Epidemiology and End Results (SEER) reporting areas.

METHODS: Incidence of unstaged invasive cancers for primary sites that have a staging scheme was analyzed for the years 1992-2011. JoinPoint regression was used to describe incidence rate trends of unstaged cancers, with analysis stratified by cancer site and by socioeconomic and demographic variables.

RESULTS: From 1992 to 1996, 8.6% of invasive cancers were unstaged. A steep decline in the incidence of unstaged cancers, represented by an annual percent change (APC) of -9.16%, was observed from 1997 to 2001, followed by a modest decline. By the end of the study period, 2007-2011, unstaged cancers represented 4.9% of invasive cancers. Unstaged cancers are disproportionately more common for older individuals and those in lower socioeconomic communities.

CONCLUSION: The incidence of unstaged cancers decreased markedly over the period studied. Change in ability to assign stage was seen, possibly related to increased use of advanced imaging like PET scans, and should be considered when evaluating changes in cancer stage distributions over time.