New perspectives on health disparities in breast cancer research

November 28, 2007

ATLANTA - Breast cancer is a disease with a number of known genetic and behavioral risk factors, but scientists have seen that these risks are often compounded by social and racial inequalities. The question remains: how, exactly, do social disadvantages, genetics, race and culture add to the disparities faced by so many groups of women?

These are among the questions in breast cancer research that scientists are addressing this week at the American Association for Cancer Research conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved, being held November 27-30 in Atlanta.

Today researchers present findings on how poverty can affect cancer prognosis, how ethnicity affects medical care and how genetics can affect the survival of different groups of women.

Racial disparities in early breast cancer outcomes in a mammographic screened population, Abstract no. A-45:

In a retrospective study of women with stage I or II invasive breast cancer, researchers at the University of Chicago have evidence that race-specific biology may contribute to the health disparity faced by African-American women. At eight years following a breast-conserving lumpectomy and radiotherapy, 78.1 percent of African-American women were free of disease versus 84.9 percent of non-black women of various ethnic groups. The researchers believe their data suggest that modification of the current screening mammography guidelines for breast cancer may benefit African Americans.

"All other things being equal, including age, the presence of co-morbid disease, socioeconomic status, weight, and tumor size, African-American women in our sample were at a disadvantage for disease-free survival of breast cancer," said Michael A. Nichols, M.D., Ph.D., a resident in the Department of Radiation Oncology at the University of Chicago.

According to Nichols, their study offers reasons to reassess how African-American women are screened and treated for breast cancer. "Our data suggests that although screening mammograms detect tumors of similar size, it appears that the advantage gained by early detection is relatively less in African-American women," Nichols said. "This study merits further evaluation of whether African-American women would benefit from either more frequent mammograms or the use of more sensitive screening methods, such as MRI."

The University of Chicago study began in 1986 and, in the ensuing decades, encompassed 1,246 women, aged 40 and above, treated at University of Chicago Hospitals and affiliates. The women enrolled had either stage I or II cancer, and they were all treated by lumpectomy and radiotherapy. About one third of participants were African-American, and they were more likely to present with large tumors and cancer that was detectable in the lymph nodes. The researchers determined socioeconomic status by patient's zip code and co-morbid diseases by patient report. Patients voluntarily defined their own ethnic status.

Nichols and his colleagues compared the African-American women to all other women enrolled in the study. When the researchers accounted for poverty and co-morbidity -- diseases such as hypertension, chronic pulmonary obstructive disease, coronary artery disease and diabetes -- race remained an independent trait that indicated poor prognosis for women with breast tumors detected through mammogram. Nichols cautioned that although the study controlled for many known prognostic indicators, it did not account for all. "Our study did not include important known contributors including the status of the Her2 gene or detailed information regarding hormonal therapy," Nichols said.

Overall survival was worse for African-American women (78.1 percent versus 84.9 percent). In addition, disease-free survival, that is, survival without relapse eight years after treatment was also worse for African-American women - 31.6 percent of African-American women experienced relapse versus 14.9 percent of all other women.

"If early breast cancer is more aggressive in African-American women, they may benefit from earlier detection than is previously obtained by yearly screening mammograms," Nichols said. "These results should offer hope to the healthcare community, because improved, more vigilant, screening may offer a simple way to improve outcomes for African-American women with early breast cancer."

Physician perspectives on surgical treatment disparities among Asian women with early stage breast cancer, Abstract no. A-54:

According to the oncologists who treat them, Asian women with early stage breast cancer are influenced by cultural factors when they decide to choose mastectomy over breast-conserving lumpectomy, even though a lumpectomy might offer a better quality of life, say researchers at the Northern California Cancer Center (NCCC), located in Fremont, California.

An Asian patient's attitude that the breast doesn't need to be preserved − primarily because of the culture's reduced emphasis on the breast and breast appearance − is an important consideration that leads many Asian women to choose a mastectomy, said a majority of physicians who participated in the investigators' survey.

Other reasons cited by physicians are that Asian women may choose a mastectomy because breast size in this population is smaller to begin with, so there is less breast to preserve, as well as factors such as age and unwillingness to travel for chemotherapy and radiation treatments which often are necessary following a lumpectomy.

Reasons for why Asian women choose mastectomy are important, say the NCCC team, because in order for a breast cancer patient to make the best clinical decision, she must be thoroughly educated on the benefits of each procedure. "For patients with early stage breast cancer where there are no clear clinical contraindications to breast-conserving treatment, a lumpectomy is less invasive than a mastectomy and it offers the same survival and potentially improved quality of life," said Jane T. Pham, an epidemiologist at NCCC and doctoral candidate in epidemiology at University of California, Davis.

In earlier research, the investigators found that a statistically significant greater number of Asian women (67.5 percent) choose to have a mastectomy over lumpectomy compared to Caucasian women (57.3 percent). And while the use of mastectomy has fallen among most populations over the past decade, it has not fallen as fast among Asian women, Pham says.

Under the direction of lead investigator Scarlett Lin Gomez, Ph.D., research scientist at NCCC and associate director of the Greater Bay Area Cancer Registry, Pham and her colleagues surveyed 80 physicians in the region who treat Chinese, Vietnamese and Filipina breast cancer patients. The survey asked physicians why they felt Asian women were choosing mastectomy significantly more often than other women.

While 74 percent of physicians surveyed said that consideration of cosmetic result is usually important to women treated with lumpectomy, most of the physicians felt cultural factors, such as a reduced emphasis on breast preservation, are the primary reasons for the higher rate of mastectomies among Asian women. Physicians also listed fear, both of reoccurrence and of radiation and chemotherapy, as another contributing factor.

All of these findings need to be probed further with Asian patients themselves, and this study is currently ongoing, Pham says. Funding for these continuing studies was provided by grants through the California Department of Health Services, National Cancer Institute and Centers for Disease Control and Prevention.

"Is it really a reduced significance of the breast when making treatment decisions, or is it fear about adverse outcomes?" Pham asked. "Although many of these cultural factors require additional research, awareness of these factors can allow physicians to directly address Asian patient concerns that may be influenced by culture, and fully inform the patient of their treatment options."

Obesity and risk for relapse of breast cancer in women of low socioeconomic status, Abstract no. A-34:

In one of the largest racially diverse studies of low income women, researchers found that women who are overweight or obese at the time they are diagnosed with breast cancer are at an increased risk of relapse.

Investigators from the Feist-Weiller Cancer Center at Louisiana State Health Science Center found that for each point gain of body mass index (BMI), the risk of cancer recurrence increased by four percent. For example, a breast cancer patient with a BMI of 30 had a 20 percent greater risk of relapse than a patient with a BMI below 25. (A BMI of 25-30 is considered overweight, and a BMI of 30 or greater is classified as obese.)

Not only was this risk evident in postmenopausal women, the researchers say, but the risk was present in premenopausal women, too. "We find that obesity, which is associated with poverty, is a significant factor in whether cancer recurs," said Amanda Sun, M.D., Ph.D., the study's lead investigator and oncologist at the Feist-Weiller Cancer Center. "The good news is weight is potentially a controllable risk factor

The research team examined medical records for 349 women diagnosed with breast cancer from 1990 to 2004. Forty-five percent of participants were African-American, and the rest were Caucasian, making the study one of the largest with a high proportion of African-American breast cancer patients, Sun says. In this group, 25 percent lived in counties with high poverty rates; 20 percent of the patients received free health care; and 25 percent were enrolled in Medicaid.

"Poverty is an important marker for limited access to healthcare, late stage disease, and worse outcomes, and the fact is that poor adults are more likely to be obese," said Dolly Quispe, M.D., hematology-oncology fellow at the Feist-Weiller Cancer Center "The goal here is to determine if there is a correlation of obesity and poverty with breast cancer recurrence, and to quantify it."

African-American patients in this study were 62 percent more likely to have limited economic means, 88 percent more likely to be overweight and obese, and 46 percent more likely to be pre-menopausal, the researchers found.

Breast cancer recurred in 69 patients, and after investigators adjusted for body weight, race, menopausal status, age at diagnosis and cancer stage, BMI at diagnosis remained a statistically significant predictor of cancer recurrence. According to Quispe, low social economic status was a marginally significant predictor of relapse after adjusting for other factors. "We can see the relationship between poverty, obesity, and cancer recurrence in this study," Quispe said

Also of note is the finding of a high rate of cancer relapse in younger patients, says Sun, "Many studies have found that obesity in postmenopausal women is a risk factor for breast cancer development, but those few that correlate excess body weight and cancer in premenopausal women have been mixed," Sun said.

The researchers say this kind of study was possible at the Feist-Weiller Cancer Center because that health center provides medical care to a significant portion of poor patients in Louisiana, a state with a poverty rate of 20 percent.

"This is a snapshot of breast cancer incidence in people without insurance," Quispe said. "It tells us that interventions targeting weight control could potentially improve outcomes in breast cancer."

The study was funded by the Feist-Weiller Cancer Center at LSU Health Sciences Center.

Disparities in receipt of lymph node assessment among early stage female breast cancer patients, Abstract no. A-65:

Examining nearby lymph nodes while a woman is undergoing surgery for early stage breast cancer is a recommended practice to determine whether the cancer has spread, although there are valid clinical reasons to omit this procedure. However, researchers at the American Cancer Society (ACS) have found that 11 percent of almost 200,000 patients in a national sample of individuals with cancer did not undergo the procedure, and these women were significantly more likely to be elderly or African-American, have no health insurance or live in an area whose residents have a low level of education.

The findings are concerning because they suggest clinical factors may not be the primary basis for decisions on breast cancer care for some disadvantaged patients, as they should be, researchers say.

"We found that significant disparities exist in who received axillary lymph node assessment, and without this procedure, an oncologist cannot appropriately stage a woman's cancer and determine optimal therapy," said Michael Halpern, M.D., Ph.D., strategic director of Health Services Research for the ACS.

Investigators specifically found that women without insurance were 24 percent less likely to receive the lymph node assessment compared to those with private insurance. Women who lived in areas with low levels of education were 13 percent less likely than those from high education areas, and African-American patients were 10 percent less likely to have the procedure than white patients.

They also found that age was a "huge" factor in who received a lymph node assessment: women age 73 or older were three times less likely to receive the procedure than were patients age 51 or younger, researchers said.

Standard practice guidelines for axillary node dissection during lumpectomy or mastectomy surgery specify when this procedure can be considered optional, such as for elderly patients, patients with other serious illnesses, or patients for whom lymph node results wouldn't affect choice of therapy.

"Ideally, factors such as race and insurance status shouldn't play any role in who receives this procedure, yet that is what we found. And while age is an important factor in deciding whether or not to perform lymph node assessments, we certainly didn't expect a three-fold difference," Halpern said.

Other studies have indicated that disparities in care may result from three different sources: structural barriers (such as health insurance or type of hospital), physician/clinical factors, and patient factors. "All three of these may be important in the disparities we observed for axillary node dissection," Halpern said.

"These disparities could result from differences in sites of care or practice patterns among healthcare providers that predominantly treat poor or uninsured women, or could reflect appropriate application of clinical guidelines in some cases," Halpern said. "We can't be sure why these disparities occur, because we just don't know how those decisions are being made at the patient and physician levels."

To conduct the study, researchers examined data from 196,732 patients who had surgery to treat early stage breast cancer from 2003-2005 from the National Cancer Database, a hospital-based registry sponsored by the ACS and the American College of Surgeons. All of these hospitals had cancer programs accredited by the Commission on Cancer; approximately 70 percent of cancer patients nationwide are treated at these hospitals.

"We need to find out why these disparities exist and what to do to make sure that everyone is getting excellent cancer care," Halpern said.
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 nearly 26,000 basic, translational, and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and more than 70 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 more than 17,000 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.

American Association for Cancer Research

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