Introduction: Race, ethnicity, and socioeconomic status are known to influence staging and survival in colorectal cancer (CRC). It is unclear how these relationships are affected by geographic factors and changes in insurance coverage for CRC screening. We examined the temporal trends in the association between sociodemographic and geographic factors and staging and survival among Medicare beneficiaries.
Methods: We identified patients 65 years or older with CRC using the 1991-2010 Surveillance, Epidemiology, and End Results-Medicare database and extracted area-level sociogeographic data. We constructed multinomial logistic regression models and the Cox proportional hazards models to assess factors associated with CRC stage and survival in 4 periods with evolving reimbursement and screening practices: (i) 1991-1997, (ii) 1998-June 2001, (iii) July 2001-2005, and (iv) 2006-2010.
Results: We observed 327,504 cases and 102,421 CRC deaths. Blacks were 24%-39% more likely to present with distant disease than whites. High-income areas had 7%-12% reduction in distant disease. Compared with whites, blacks had 16%-21% increased mortality, Asians had 32% lower mortality from 1991 to 1997 but only 13% lower mortality from 2006 to 2010, and Hispanics had 20% reduced mortality only from 1991 to 1997. High-education areas had 9%-12% lower mortality, and high-income areas had 5%-6% lower mortality after Medicare began coverage for screening colonoscopy. No consistent temporal trends were observed for the associations between geographic factors and CRC survival.
Discussion: Disparities in CRC staging and survival persisted over time for blacks and residents from areas of low socioeconomic status. Over time, staging and survival benefits have decreased for Asians and disappeared for Hispanics.