DETERMINANTS OF BLACK-WHITE DIFFERENCES IN COLON-CANCER SURVIVAL

Background: Blacks have lower survival rates for colon cancer than whi tes, possibly related to more advanced stages of disease at diagnosis and to socioeconomic differences between blacks and whites, White the black/white difference in colon cancer survival is well documented, th e few studies that have investigated this difference have been limited by the modest number and type of explanatory factors that were consid ered, Purpose: We analyzed data from the National Cancer Institute Bla ck/White Cancer Survival Study to determine 1) what characteristics mi ght contribute to the racial difference in colon cancer survival and 2 ) if a survival disparity remained between black and white patients af ter adjustment was made for these characteristics. Methods: This prosp ective study included 454 blacks and a stratified random sample of 521 whites, aged 20-79 years, with cancer of the colon diagnosed from Jan uary 1, 1985, through December 31, 1986, and who were residents of the metropolitan areas of Atlanta, New Orleans, and San Francisco/Oakland , Follow-up was truncated on December 31, 1990, Cox proportional hazar ds regression was used to estimate the death rate among blacks relativ e to that among whites after adjustment for potential explanatory fact ors, including sociodemographic factors, concurrent (comorbid) medical conditions, stage at diagnosis, tumor characteristics, and treatment, All P values were calculated from two-tailed tests of statistical sig nificance, Results: After adjustment for age, sex, and geographic area , the black-to-white mortality hazard ratio (HR) was 1.5 (95% confiden ce interval [CI] = 1.2-1.9), indicating that the risk of death among b lack patients was 50% higher than that among white patients, Further a djustment for stage reduced the excess cancer mortality to 20% (HR = 1 .2; 95% CI = 1.0-1.5), decreasing the overall racial difference in exc ess mortality from 50% to 20% or to a 60% reduction in excess mortalit y, Although adjustment for poverty reduced the excess mortality by 20% , adjusting for both stage and poverty did not further reduce the raci al difference, Among patients with stages II and III disease, blacks h ad 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 met astatic disease (stage IV), survival was similar for whites and blacks , Conclusions: Stage at diagnosis accounted for more than half of the excess colon cancer mortality observed among blacks, Poverty and other socioeconomic conditions, general health status, tumor characteristic s, and general patterns of treatment did not further explain the remai ning survival disadvantage among blacks, Implications: Because the rac ial disparity was confined to earlier stages, future studies should in vestigate whether blacks have more advanced disease at diagnosis and w hether less aggressive treatment is provided because of understaging,