However, a study published in tomorrow's Journal of the American Medical Association sheds new light on the topic, and points to underlying medical problems as a big reason for the disparity in death rates.
"Our analysis indicates that perhaps the main reason why blacks die of cancer so much more frequently than whites has more to do with their increased risk of other health problems, such as diabetes and heart disease, than it has to do with either the cancer itself or the treatment they receive," says study author Dr. Peter Bach, an epidemiologist and biostatistician at Memorial Sloan-Kettering Cancer Center in New York City.
There's no shortage of theories on the disturbing trend.
One points the finger at genetics. Here, researchers hint that perhaps blacks develop a more aggressive form of cancer -- one that does not respond as well to treatments that were, by and large, tested on white men.
A second proposes that blacks simply receive a lower quality of care -- with cancers diagnosed later, at more deadly stages.
While Bach admits both these tenets may be true to some extent, he does not believe they represent the overriding reason for the increased cancer death rate among blacks.
"When we looked at survival statistics for those who had been treated the same, with similar stage disease, we found the aggressiveness of the cancer was similar in blacks and whites, and response to treatment was similar," Bach says.
The only factor that seemed to make a difference, he adds, is the increased incidence of underlying health problems such as diabetes and heart disease.
"What we are saying is that, from a public health standpoint, we need to place our focus not on looking for genetic differences, but instead in finding ways to improve the overall health care of blacks, so that there is less underlying disease and that, we believe, will translate into lower cancer-related death statistics across the board," Bach says.
That idea was supported by the study results. When both races received comparable care for similar stage cancers, blacks appeared to be about 16 percent less likely to survive than whites. However, when the authors applied a mathematical formula to estimate the death rates for these same patients due to health problems other than cancer, much of the disparity between the two groups faded.
Survival rates for the three most deadly cancers -- prostate, lung and colorectal -- were almost identical among blacks and whites, Bach says. The same was true for nearly all 14 of the cancers examined in the study.
"After we analyzed death rates from other causes, the overall increased risk of cancer death for blacks as compared to whites was just 7 percent. And this difference was concentrated in just three cancers -- breast, uterine and bladder cancer, of which the last two are relatively rare," Bach says.
However, an editorial accompanying the study says the quality-of-care issue still looms large.
"[The study] used only a crude measure of comparitability of care across ethnic lines, based on participation in randomized trials and similarity of major inventions (chemotherapy, surgery)," says Dr. Catarina I. Kiefe, of the University of Alabama at Birmingham. "The findings by no means exclude the possibility of care actually not having been comparable for blacks and whites."
The study itself involved a review of all English-language medical articles published over a 35-year period, from 1966 through January 2002. The articles identified 89 patient groups from 54 individual and different studies involving a total of 189,877 whites and 43,004 blacks. The studies also included 14 different cancers.
After applying the new mathematical analysis to estimate death rates due to health problems other than cancer, a statistical picture emerged showing nearly equal survival rates among both races.
"Based on this research, I don't believe there is much evidence to show that cancer is genetically or biologically different in blacks than in whites, and that it is likely to be that factors outside the realm of the disease itself are influencing the rate of death and causing the racial disparity," Bach says.
Kiefe agrees to a point: "Although attributing these disparities to biological differences might partially absolve physicians from the need to address them, the scientific underpinnings for this attribution are weak."
It would be far more fruitful to look for problems at the level where care is delivered, Kiefe says, which may also be the easiest to change.