The Uninsured are a Distinct Population in a Breast Cancer Cohort, with Unique Screening, Staging, and Outcomes.

Insurance status is a known determinant of cancer stage at diagnosis and outcome. However, insurance status can change over the course of the disease and its treatment, complicating causal analysis. Cancer registries strive to capture the insurance status of patients at diagnosis, but this is not always possible. Breast cancer poses a particular challenge for this effort, as uninsured patients become eligible for Medicaid upon the diagnosis. Thus, their insurance status may have changed from uninsured to Medicaid by the time registrars interact with treatment records. We addressed this potential blurring between categories by working with a sample of patients identified through the cancer registry of the Medical University of South Carolina to focus on determining insurance status at diagnosis whenever possible. We found that the uninsured population (32 women) was larger than the Medicaid-covered population (22 women) in a sample of patients in South Carolina, a state that did not accept the Medicaid expansion. Compared with women who carried any type of insurance, uninsured women were much more likely to find their own breast mass through palpation rather than through screening, they were diagnosed with a later stage of breast cancer at diagnosis, and their outcomes were worse. Insured women experienced significantly increased survival odds (odds ratio, 3.28) and multiple regression analysis demonstrated that the higher stages seen in uninsured women largely accounted for the poorer outcomes. These findings suggest that more research is needed to define the characteristics and disease courses unique to the breast cancer population lacking insurance prior to diagnosis.