A new study by researchers at the Fred Hutchinson Cancer Research Center in Seattle has documented important differences in breast-cancer diagnosis, treatment and survival for American women of various racial and ethnic backgrounds.

The findings, reported in the journal Archives of Internal Medicine, are based on the most comprehensive study of its kind, in which data was evaluated from nearly 125,000 women representing all major racial/ethnic populations and subpopulations in the United States first diagnosed with breast cancer between 1992 and 1998.

Stage of disease:

Blacks, Native Americans and Hispanic whites were more likely to be diagnosed with tumors that were more advanced than were non-Hispanic whites and Asians/Pacific Islanders. Specifically, blacks, Hispanic whites and Native Americans faced a 1.7 to 2.5-fold higher risk of being diagnosed with later-stage tumors and Puerto Rican women fared the worst, with a 3.6-fold increased risk of being diagnosed with late-stage breast cancer. Japanese women were 30 percent less likely to be diagnosed with late-stage breast cancer.

Treatment:

Puerto Rican women fared the worst, as they were 50 percent more likely to receive substandard, inappropriate treatment for breast cancer. Black women were 40 percent more likely to undergo initial treatment for breast cancer that was below national standards as compared to non-Hispanic whites. Japanese, Filipino, Chinese, Korean and Vietnamese women were all more likely to receive appropriate care.

Survival:

Japanese and Chinese women had better survival rates after breast cancer while blacks, Native Americans and Hispanic whites faced a 10 percent to 70 percent greater risk of dying after a breast-cancer diagnosis as compared to non-Hispanic whites.

While underlying biological differences among the ethnic groups could be a contributor to the disparities, lead researchers Dr. Christopher Li suspects that lack of access to health care is the largest factor behind the increased mortality rates for African Americans, Native Americans and Hispanics.

''In our analysis we adjusted for stage of disease, hormone-receptor status of the tumors and the types of treatment the women received. Even after adjusting for these factors, these groups of women were still more likely to die of breast cancer,'' Li said.

''The results of our study and other recent reports strongly suggest that socioeconomic factors are a much larger contributor to poor breast-cancer outcomes among certain racial/ethnic groups than are biologic or genetic factors," he added.

Other sources: Fred Hutchinson Cancer Research Center, Archives of Internal Medicine