Residential history in cancer research: Utility of the annual billing ZIP code in the SEER-Medicare database and mobility among older women with breast cancer in the United States

There is a rise in attention to residential history in cancer epidemiology aimed at more effective estimation of social and physical environmental exposures and the influence of place of residence on cancer outcomes. However, in the United States, as in many other countries, residential history data are not readily available. In this paper we explore the feasibility of using the annual Medicare billing ZIP code history available in the SEER-Medicare database to study residential mobility among older cancer survivors in the U.S. In a cohort of women diagnosed with breast cancer between 2007 and 2015, we examine the completeness of the data along with the overall characteristics of residential moves based on race and stage at diagnosis. Findings indicate that residential mobility among older women with breast cancer in the U.S. is limited, but differences by race/ethnicity, stage at diagnosis and before/after diagnosis are statistically significant. And breast cancer survivors from minority groups move more frequently than their non-Hispanic White counterparts. The results also show that move rate slightly, but statistically significantly, increases after diagnosis. We conclude that SEER-Medicare can be utilized to study residential mobility among older cancer survivors. We recommend the creation of sub-cohorts based on specific research questions to account for variability in residential mobility due to very short survival times or a diagnosis shortly after Medicare enrollment. Studying residential history provides the opportunity for assigning socioecological and exposure metrics for future survival studies.