Inequality trends in proximal and distal colon cancers.

Abstract

565 Background: Recently, the USPHTF released new colon cancer screening guidelines. No priority was given to any screening method. Given studies showing that Blacks had a greater proportion of proximal cancers, we sought to better highlight the inequalities in outcomes in order to consider the appropriateness of sigmoidoscopies versus colonoscopies. Methods: The SEER database was utilized to pull incidence and 5 year relative survival data (1992-2013). Patients aged 50-84 were divided by race and percentage of a county’s population below the poverty line ( < or > 15%). Adenocarcinomas were divided between distal cancer in the sigmoid, rectum, and anus versus cancer in the remainder of the colon. This data was analyzed using HDCalc, modelling rate difference, rate ratio, and the Index of Disparity. The Joinpoint regression program was then used to model Average Annual Percent Change (AAPC). Results: The AAPC in distal cancer incidence among Whites (-3.2%, [95% CI = -3.5%, -2.8%], p < 0.05) was greater than in Hispanics (-1.6%, [95% Cl = -2.1%, -1.1%], p < 0.05), or Blacks (-2.3%, [95% CI = -2.9%, -1.8%], p < 0.05). This resulted in a decline in the Index of Disparity (AAPC: -6.6, [95% Cl: -9.1, -4.0], p < 0.05) largely due to Whites' greater gains relative to Hispanics (Rate Ratio AAPC: -1.6%, [95% Cl: -1.9%, -1.3%], p < 0.05). Less impressive were AAPC trends in proximal cancers, which were significant in Whites (-1.8%, [95% CI: -2.2%, -1.5%], p < 0.05) and Blacks (-1.3%, [95% Cl: -1.8%, -0.8%], p < 0.05). Additionally, the AAPC for proximal cancer’s Index of Disparity was also lower (-3.1%, [95% Cl: -3.8%, -2.4%], p < 0.05). In terms of survival, only distal cancer’s AAPC for its Index of Disparity was significant (-3%, (95% Cl: -5%, -1.1%), p < 0.05). Poorer counties performed worse in incidence reduction across races but similarly in survival improvements. Conclusions: While it is encouraging to see improvements in distal colon cancer outcomes, it is troubling to see that measures in proximal cancers are lagging behind. The slower improvements among the Black population and higher baseline mortality and incidence of such cancers would seem to indicate a need to further study the comparative value of more aggressive screening, particularly in this group.