Important disparities in breast-cancer diagnosis, treatment and survival among American women of various racial and ethnic backgrounds are documented in a new Fred Hutchinson study.
These findings by Drs. Christopher Li, Janet Daling and Kathi Malone in the Public Health Sciences Division, published Monday in Archives of Internal Medicine, are based on the largest, most comprehensive study of its kind to evaluate the relationship between race/ethnicity and breast-cancer stage, treatment and survival.
The study evaluated data from nearly 125,000 women representing all major racial/ethnic populations and subpopulations in the United States, the majority of whom have been tracked by national cancer registries only since the late 1980s.
"Numerous studies have evaluated the relationship between race and ethnicity and breast-cancer treatments and outcomes, but most have crudely divided the data into broad heterogeneous categories, such as Asians/Pacific Islanders and non-Hispanic whites," Li said.
"This study, in contrast, evaluated several subgroups of these populations and found important differences among them.
"There is reason to believe that there would be differences in breast-cancer outcomes based on diverse cultural practices, dietary habits and, possibly, genetics, but socioeconomic factors are likely to play the most important role."
Among Asian/Pacific Islanders and Hispanic whites, Li and colleagues uncovered significant differences in stage at diagnosis, treatment and outcome among women in various racial/ethnic subcategories, including Japanese, Filipino, Indian/Pakistani, Mexican and Puerto Rican. Japanese women fared best overall. For example:
Stage of disease: Japanese women were 30 percent less likely to be diagnosed with late-stage breast cancer compared to non-Hispanic white women, while women of Filipino, Hawaiian, Indian-Pakistani, Mexican, South and Central American, and Puerto Rican descent were 20 percent to 260 percent more likely to be diagnosed with late-stage breast cancer.
Treatment: While Mexican and Puerto Rican women were more likely than non-Hispanic whites to receive inappropriate treatment for breast cancer, 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 Hawaiian and Mexican women had 30 percent poorer survival rates when compared to non-Hispanic whites.
"Japanese women may have better outcomes based on their longer history of living in the United States," Li said. "They're less likely to be recent immigrants than others within the Asian community, such as Koreans and Vietnamese. Recent immigrants have less access to care and may have more difficulty getting care due to language barriers and other acculturation issues."
Data for the study was obtained from 11 population-based tumor registries from racially and ethnically diverse communities throughout the United States, all of which are part of the Surveillance, Epidemiology and End Results (SEER) program, a national cancer registry operated by the National Cancer Institute.
The researchers analyzed medical data from 124,934 women from Seattle, San Francisco/Oakland, Los Angeles, San Jose, Atlanta and Detroit, as well as Connecticut, Hawaii, Iowa, New Mexico and Utah. All of the women were first diagnosed with breast cancer between 1992 and 1998.
Cases were divided by race or ethnicity into 17 categories, including 12 subcategories of large ethnic populations that were added to the SEER registry in 1988.
"Thanks to the recent stratification of the SEER data, we were able to look at eight subgroups of Asians/Pacific Islanders and four subgroups of Hispanic whites in addition to non-Hispanic whites, African Americans and Native Americans," Li said.
With the newly expanded cancer-registry data at their disposal, the researchers confirmed what many smaller, less ethnically and geographically diverse studies have suggested regarding the significant disparities in breast-cancer diagnosis, quality of care and outcome among various U.S. racial and ethnic groups.
"One of the most disturbing trends identified by our research is that we have known since the 1970s that certain racial/ethnic groups, such as African-Americans, have poorer breast-cancer outcomes," Li said. "Even though we've recognized this for some time, the trend persists. Despite having several decades to improve this situation, it remains an important problem."
Lack of health-care access
While underlying biological differences among ethnic groups could be a contributor, Li and colleagues suspect 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," he said. "Even after adjusting for these factors, these groups of women were still more likely to die of breast cancer.
"This means that disparities in outcomes are likely due to other issues, such as access to care and socioeconomic status.
"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. Socioeconomic factors theoretically are much more reversible than biological or genetic phenomena. Thus, these findings present a challenge to society, because these discrepancies in outcomes are preventable."
Li conducted the research under a Cancer Epidemiology Training Grant while completing a postdoctoral fellowship in the University of Washington School of Public Health and Community Medicine, where he is an assistant research professor of epidemiology.
Other highlights of study
Other highlights of the findings by Dr. Chistopher Li and PHS colleagues fall into three categories:
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.
Again, 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.
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.