Racial Disparities in Colon Cancer Survival Linked to Advanced Disease and Comorbidities at Diagnosis

Key Points

  • Disparities in the 5-year survival rate between black and white patients with colon cancer appears to be related more to advanced stage of disease at diagnosis and comorbid conditions rather than differences in subsequent treatment.
  • Focusing efforts on prevention and early detection strategies may close the gap in racial disparities in colon cancer survival.
  • According to the American Cancer Society, the 5-year relative survival rate for colorectal cancer among African Americans is 57% vs 65% among whites.

Racial disparities in colon cancer survival rates may be explained by differences in the health of the patients at diagnosis—both in the stage of the cancer and comorbid conditions—rather than by differences in subsequent treatment, a new study has found. Focusing efforts on prevention and early detection strategies may close the gap in racial disparities in colon cancer survival. The study by Silber et al is published in the Annals of Internal Medicine.

Study Methodology

The objective of this study was to determine the relative contributions of disease presentation at diagnosis and treatment after diagnosis to differences in the 5-year survival rates between black and white patients with colon cancer. The researchers analyzed patient data from the Survey, Epidemiology, and End Results (SEER)-Medicare Database for the years 1991 to 2005. The patients were aged 65 years or older with newly diagnosed invasive colon cancer.

A total of 7,677 black patients were matched with three groups of 7,677 white patients. The patients were matched based on demographic characteristics, such as age, sex, and year of diagnosis; a “presentation” match controlling for demographic characteristics plus comorbid conditions and tumor characteristics, including stage and grade; and a “treatment” match, which included presentation variables plus details of surgery, radiation, and chemotherapy. The patients were followed until December 2009.

Study Findings

The researchers found the absolute difference in 5-year survival between black and white patients was 9.9% (95% confidence interval [CI] = 8.3%–11.4%; P < .001) in the demographic characteristics match. This disparity remained unchanged between 1991 and 2005. After matching for presentation characteristics, the difference decreased to 4.9% (95% CI = 3.6%–6.1%; P < .001). After additional matching for treatment, this difference decreased to 4.3% (95% CI = 2.9%–5.5%; P < .001). The disparity in survival attributed to treatment differences made up an absolute 0.6% of the overall 9.9% survival disparity.

“More of the racial disparity in colon cancer survival is explained by differences in health at diagnosis (both the state of the cancer and comorbid conditions) than by differences in subsequent treatment,” concluded the researchers. “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.”

According to the American Cancer Society, the 5-year relative survival rate for colorectal cancer among African Americans is 57% vs 65% among whites.

Jeffrey H. Silber, MD, PhD, of The Children’s Hospital of Philadelphia, is the corresponding author for the Annals of Internal Medicine article.

Funding for the study was provided by grants from the Agency for Healthcare Research and Quality and the National Science Foundation. For full disclosures of the study authors, view the study abstract at www.annals.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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