Reviewing the data from cancer outcome studies published over the past thirty-five years, a team of researchers led by scientists at Memorial Sloan-Kettering Cancer Center found that when black and white cancer patients received equal treatment, i.e. comparable care at a similar stage of disease, blacks still had a slight survival disadvantage. However, once deaths from all other health causes were considered, survival was basically the same.
This finding casts doubt on one of the popular explanations for the racial gap in survival-that cancer behaves more aggressively in blacks due to biologic or genetic differences. These findings were published in The Journal of the American Medical Association.
"In many studies, survival differences between blacks and whites with cancer persisted after adjustment for factors like disease stage and socioeconomic status, suggesting that there was some biologic or genetic difference between the racial groups," explained Dr. Peter Bach of the Department of Epidemiology and Biostatisticsat Memorial Sloan-Kettering and the study's first author." In our study, we took a hard look at this issue determine if the poorer survival in blacks was due to other causes like heart attack, stroke or diabetes, rather than more aggressive cancer."
The study was conducted to determine if there was evidence in the literature of racial disparities in survival where blacks and whites had received the same treatments for cancer at the same stage. A review of all English-language articles published from 1966 to January 2002 that described outcomes for black and white cancer patients identified 89 cohorts from 54 individual studies representing 189,877 white and 32,004 black cancer patients and included fourteen different cancers.
Looking at survival data, blacks that received comparable treatment for similar stage cancers were at a 16 percent increased risk of death relative to whites. The authors then developed a mathematical model to estimate the death rates for these same patients due to health problems other than cancer. Much of the survival disparity could be attributed to non-cancer related deaths. After this correction, the increased risk of death for blacks was halved to 7 per cent.
The researchers also examined several types of cancer and found the survival gap between blacks and whites for most cancers including the major killers - lung, prostate and colorectal - was eliminated once the correction for deaths due to other causes was taken into account. However, of the 14 cancers examined, blacks were at a higher risk of cancer death in a small number of cancer types: breast and two relatively rare cancers -uterine and bladder. The authors note the importance of additional research in this area.
"There is not much evidence that cancer behaves differently in blacks than in whites. Differences in treatment, stage of disease at presentation, and mortality from other diseases - not biologic or genetic differences - seem to explain most of the disparity." said Colin Begg, Ph.D., chairman of the Department of Epidemiology and Biostatistics at Memorial Sloan-Kettering and senior author of the study. "These are the areas that should be the primary targets for future research and public health interventions."
SOURCES:
Journal of the American Medical Association, April 24, 2002; 287:2106-2113
Memorial Sloan-Kettering Cancer Center (http://www.mskcc.org)
