Racial Disparities in Cancer Not as Simple as Black and White
April 2, 2006
Field(s) of Research
: Epidemiology, Prevention Research
WASHINGTON, D.C. -- African-Americans are more likely to develop cancer and to die from this disease than any other racial or ethnic group in the U.S. population. The cancer death rate among African-America men is 40 percent higher than that of white men; it is 14 percent higher in black women. Possible causes for this discrepancy include lack of health insurance, poverty, language and cultural barriers, and inadequate access to early detection services and good medical care. Research reported today at the 97th Annual Meeting of the American Association for Cancer Research (AACR) suggests that genetics, in addition to socioeconomic status, are important factors accounting for the disparity of cancer incidence and mortality between African-Americans and whites.
Underserved African-American and White Women with Breast Cancer Have Similar Prognostic Profiles for Estrogen Receptor and Tumor Grade: Abstract No. 3696
The racial disparity in breast cancer prognosis and survival may have more to do with socioeconomic status, rather than biological factors, according to a study of women diagnosed and treated at a public hospital. Though the population sample was relatively small, including 341 African-American and 94 white women, the results suggest that low economic standing contributes to similarly poor prognostic profiles for tumor grade and estrogen receptor status in both races, according to the researchers.
“This is the first study of its kind in the U.S. based on data from a single institution,” said Keith A. Dookeran, M.B.B.S, FRCS (Ed), leader of the research team at the Minority-Based-Community Clinical Oncology Program at Stroger Hospital of Cook County. “Most of the other studies of the apparent difference in breast cancer prognosis between African-American and white women drew on data from many different geographic areas.”
When Dookeran and his team narrowed the study population to patients at a single, public institution, and adjusted the data for age and stage of disease, they found no significant difference in tumor grade or estrogen receptor status between white and African-American women.
“Cook County Hospital is a public hospital,” Dookeran said. “The women here are largely uninsured and of low socioeconomic status, and they appear to have similar prognostic indicators with high-grade and ER-negative tumors, be they African-American or white.”
“Our results suggest that low socioeconomic status, regardless of race, is associated with a particular tumor phenotype.” Other research attributes the poorer prognosis for breast cancer in African-American women, compared to white women, to the more frequent occurrence in blacks of high-grade, estrogen receptor negative tumors that hinder treatment options.
High-grade- and estrogen receptor-negative tumors signal an aggressive breast cancer with a lower rate of survivability. Estrogen receptor-negative tumors are so called because they do not express the genes that bind to estrogen, the hormone which plays a crucial role in the development and progression of the disease. Some of the most effective chemotherapy treatments for breast cancer act by targeting the receptors and inhibiting their ability to stimulate estrogen production in the breast.
Dookeran and his colleagues at the NCI-supported Minority-Based-Community Clinical Oncology Program at Stroger Hospital wondered whether there really is a connection between race and breast tumor biology when all the other variables were factored into the inequity equation, such as, access to preventative care and diagnostic testing; availability of health insurance; socioeconomic standing; and geographic location.
“African-American women are more commonly underserved and have low socioeconomic status (SES), and other studies suggest that SES, not simply race, is associated with this prognostic profile,” said Dookeran.
To assure a consistent standard of diagnosis and a common quality of care, Dr. Dookeran and his colleagues studied only women from the Minority-Based-Community Clinical Oncology Program at Stroger Hospital. After adjusting for age, the researchers found no significant differences between races regarding stage, ER status and tumor grade. Furthermore, disease-free, distant disease-free and overall survival were similar for both races overall, and also for ER positive subsets.
Black-white Disparities in the Recommendation and Outcomes of Adjuvant Chemotherapy Among Colorectal Cancer Patients: Abstract No. 659
Chemotherapy is recommended to treat colorectal cancer (CRC) in whites more often than in African-Americans, according to a study of more than 17,000 CRC patients of both races in Alabama.
Hanaa S. Elhefni, M.D., M.S, M.P.H., of the Wright State University in Dayton, Ohio, studied the disparity in CRC mortality rates between African-Americans and whites. According to the U.S. Centers for Disease Control and Prevention, while the five-year survival rate for whites with the disease rose to 64 percent over the last 25 years, the rate for African-Americans improved to just 55 percent during the same period.
“This disparity could be partly attributed to differences in risk factors,” Elhefni said, “but variations in medical practice may also be potential contributors.”
The study investigated patterns and trends in adjuvant chemotherapy recommendations, use and outcomes for all black and white CRC patients diagnosed between 1996 and 2002 in Alabama. Adjusting for potential confounding variables such as age, sex and stage of disease at diagnosis, Elhefni found that blacks were 20 percent less likely to have chemotherapy recommended than whites. The compliance rate for blacks and whites prescribed chemotherapy was the same.
Both African-Americans and whites benefit significantly from adjuvant chemotherapy for CRC. Five-year survival rates were significantly higher and mortality rates significantly lower among all those who received the treatment, compared to those who did not.
“Obviously, the disparity in CRC outcomes could be greatly reduced by changes in medical practice,” Elhefni said. “But it is a complex situation, not a simple matter of racial bias. More studies are necessary to identify the factors that influence physician and patient choices when faced with cancer, and to find the best ways to narrow the management/treatment and mortality gaps between the races.”
The Relation of Overall and Central Obesity to Risk of Breast Cancer in African-American Women: Abstract No. 2024
Contrary to long-held theory, obesity may not increase the risk of breast cancer among older African-American women, according to research performed at Boston University and Howard University in Washington, D.C.
However, the study confirmed previous work that younger women with a high body mass index (BMI) have a reduced risk of breast cancer. The research team, led by Julie R. Palmer, Sc.D., professor of epidemiology at the Boston University School of Public Health, focused on the relationship between breast cancer and various measures of obesity in African-American women, in particular, because the prevalence of obesity in the U.S. is highest in the black population.
There is also a tremendous amount of information available from the Black Women’s Health study, which enrolled 59,000 participants in 1995, and followed up on the health and medical status of each with biennial questionnaires.
After eight years of follow-up, 809 women reported having breast cancer—about half of them premenopausal and half postmenopausal. Whether a breast cancer occurs before or after menopause is an important consideration in light of the association between estrogen-fueled breast cell proliferation and the development and progression of breast cancer Palmer’s group confirmed the findings of previous studies that a higher BMI at age 18 decreases a woman’s risk of developing premenopausal breast cancer and, possibly, postmenopausal breast cancer as well.
“Some previous research, but not all, has shown that high body mass index among older women increases breast cancer risk,” Palmer explained. “We actually found the opposite in our study. African-American women with a BMI that qualifies them as obese did not have a higher risk of getting breast cancer. In fact, the risk was slightly lower in obese women overall, in agreement with findings from another study of black women.”
One possible explanation for the discrepancy between the findings for black and white women has to do with differences in the timing of excess weight gain, with black women, in general, becoming overweight at younger ages than white women. There is some evidence that the adverse effect of overweight on postmenopausal breast cancer risk is strongest in the decades closely following the weight gain. Indeed, in Palmer’s study, while there was no increased risk with current BMI overall, there was an association between increasing risk and increasing BMI among postmenopausal women under age 50. Their breast cancer would have developed most closely in time to their maximum weight gain.
The latest report from the American Cancer Society states that the overall rate of breast cancer is 17 percent lower in African-American women than in white women, but the five-year survival rate is 14 percent higher in blacks.
Noting the health benefits of maintaining an optimum weight, Palmer points out that her research does not change that message. “The study results may help explain why breast cancer incidence is lower in black women than white women after age 50 even though the prevalence of obesity is higher,” she said.
Racial Differences in Triple Negative Breast Tumors Among Women in Atlanta: Abstract No. LB-4
They’re commonly referred to as “triple negatives”— breast cancers characterized by three biological components that make the disease more difficult to treat. Oncologists base treatment decisions on the presence of three hormones known to fuel most breast cancers—estrogen receptors, progesterone receptors and human epidermal growth factor receptor 2, or HER2. The most effective chemotherapy agents for breast cancer, such as tamoxifen and trastuzumab (Herceptin), work by targeting these hormones. Women with triple negative tumors lack all three.
In a study of racial differences in the prevalence of triple negative invasive breast tumors, a team of researchers from Emory University in Atlanta, the Fred Hutchinson Cancer Research Center in Seattle, and the Centers for Disease Control, found the incidence of triple negative disease in African-American women to be more than twice that of white women.
“Triple negative disease has not been adequately described or studied, particularly among minority populations,” said Emory researcher Mary Jo Lund, Ph.D. “It has the worst prognosis because the tumors have the worst characteristics and preclude the use of the most common, effective treatments,” said Lund.
To assess the racial differences in the prevalence of triple negative breast cancer, Lund and her colleagues in Atlanta analyzed tumor data from Fred Hutchinson Cancer Research Center collaborator Peggy Porter, M.D., and data from their study of racial differences in progression of breast cancer among Atlanta women under the age of 55.
When the data were broken down by race and adjusted for age and stage of disease at the time of diagnosis, the team found that 47 percent of tumors in black women were negative for estrogen receptor, progesterone receptor, and HER2, compared to 22 percent in whites. There also were strong associations found in African-American women and white women between triple negative disease and high-grade tumors and abnormal expression of p53, a tumor-suppressor gene with cancer-inhibiting properties.
At all ages, African-American women are at lower risk for breast cancer compared to white women. However, for women under the age of 50, African-American women are at increased risk over white women of the same age. “There is also evidence that younger African-American women have breast tumors with more aggressive features,” said Porter.
“Additional studies are needed to examine the risk factors for triple negative tumors, and why black women have this increased risk,” said Lund. “Our results are provocative and carry the message that African-American women might be at higher risk for worse breast tumors and at an earlier age.”
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The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, AACR is the world’s oldest and largest professional organization dedicated to advancing cancer research. The membership includes more than 24,000 basic, translational, and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and more than 60 other countries. AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants. The AACR Annual Meeting attracts over 16,000 participants who share the latest discoveries and developments in the field. Special Conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment, and patient care. AACR publishes five major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. Its most recent publication, CR, is a magazine for cancer survivors, patient advocates, their families, physicians, and scientists. It provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship, and advocacy.
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