The authors analyzed data from the National Cancer Institute Black/White Cancer Survival Study to determine the characteristics contributing to the racial difference in colon cancer survival and if a survival disparity remained between black and white patients after adjustment was made for these characteristics. The prospective study included 454 blacks and a stratified random sample of 521 whites, aged 20-79 years, with cancer of the colon diagnosed from January 1, 1985, through December 31, 1986, and who were residents of the metropolitan areas of Atlanta, New Orleans, and San Francisco/Oakland.

“More than 20% (22%) of blacks and 15.4% of whites had metastases at diagnosis. A larger proportion of black patients than white patients had unknown extent of invasion (T) and were somewhat more likely to have unknown nodal status. Blacks were less likely than whites to have undergone surgery.”

“There were some differences in treatment between black and white patients with similar stages of disease. All black and white patients, however, with nonmetastatic disease (stages I-III) underwent surgery, whereas 96.3% of white patients and 89.0% of black patients with metastatic, stage IV disease underwent surgery. None of the black patients with stage I disease received adjuvant therapy, whereas 5.8% and 1.9% of white patients with stage I colon cancer received chemotherapy and radiation therapy, respectively.”

“The survival probabilities for any cause of death and for invasive colon cancer were significantly lower for black patients than for white patients.”

“After adjustment for age, sex, and geographic area, the black-to-white mortality hazard ratio (HR) was 1.5 (95% CI=1.2-1.9)… Further adjustment for stage reduced the excess cancer mortality to 20% (HR=1.2; 95% CI=1.0-1.5)….Although adjustment for poverty reduced the excess mortality by 20%, adjusting for both stage and poverty did not further reduce the racial difference. Among patients with stages II and III disease, blacks had lower survival rates than whites (HR=1.8; 95% CI=1.0-3.1 and HR=1.5; 95% CI=1.0-2.3, respectively). Among those patients with metastatic disease (stage IV), survival was similar for whites and blacks.”

“Because the racial disparity was confined to earlier stages, future studies should investigate whether blacks have more advanced disease at diagnosis and whether less aggressive treatment is provided because of understaging.”