The persistent disparity in colon cancer survival by race seemed to be related more to differences in health at diagnosis than to differences in subsequent treatment, according to an analysis of data from the Survey, Epidemiology, and End Results (SEER)–Medicare database. “Our study suggests that the most effective route to reducing the racial survival disparity is to find ways to reduce the disparity in presentation, so fewer black patients present with advanced disease,” Jeffrey H. Silber, MD, PhD, of the Center for Outcomes Research, The Children’s Hospital of Philadelphia, and colleagues wrote in the Annals of Internal Medicine.
The investigators obtained SEER–Medicare data for 1991 to 2005 for 16 SEER sites throughout the United States (including all sites except the Alaska Native Tumor Registry). A total of 7,677 black patients aged 65 years or older diagnosed with colon cancer were matched with three successive sets of 7,677 white patients with colon cancer, first on the basis of demographic characteristics, next on presentation, and then on treatment. “The three matches sequentially removed aspects of the disparity while leaving other aspects in place, so we could develop an understanding of how the disparity occurs,” the investigators noted.
The demographic characteristics match controlled for age, gender, diagnosis year, and SEER site and showed an absolute difference in 5-year survival between black and white patients of 9.9% (95% CI, 8.3%–11.4%; P < .001), which remained unchanged between 1991 and 2005. This represented a difference in median survival of 19 months.
The presentation match controlled for demographic characteristics plus comorbid conditions and tumor characteristics, including stage and grade, decreased the 5-year survival difference to 4.9% (CI, 3.6%–6.1%; P < .001), or a difference in median survival of 8 months. The treatment match included presentation variables plus details of surgery, radiation, and chemotherapy and decreased the 5-year survival difference to 4.3% (CI, 2.9%–5.5%; P <.001), or a difference in median survival of 7 months. “The disparity in survival attributed to treatment differences made up only an absolute 0.6% of the overall 9.9% survival disparity,” the investigators noted.
“The residual disparity in the treatment match is similar to the 5-year survival disparity between black and white patients in the U.S. population as a whole,” the authors observed. “Although similar, we do not suggest that this is acceptable.” ■