Women from ethnic minorities in the US are more likely to have aggressive subtypes of breast cancer and receive inappropriate treatment when compared with non-Hispanic white women, according to an article in Cancer Epidemiology, Biomarkers & Prevention - a journal of the American Association for Cancer Research.

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Quality of treatment for breast cancer is affected by ethnic origin.

Lu Chen, a researcher in the Public Health Sciences Division at Fred Hutchinson Cancer Research Center in Seattle, WA, notes that minority women, especially African-Americans, Hispanic whites and American-Indians, are consistently more likely to be diagnosed at advanced stages of breast cancer, less likely to receive recommended treatment regimens and more likely to die of the disease.

Previous studies have addressed the disparities by stage of disease and survival rates but did not characterize them by subtypes, according to Chen.

Chen's team collected data about 102,064 American women from 18 US population-based cancer registries participating in the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute.

African-American women 40-70% more likely to be diagnosed late

The information collected includes demographic characteristics, stage, tumor grade and size, primary treatment and health insurance status of the patients, as well as their tumor subtypes, hormone receptor (HR) status and human epidermal growth factor 2-neu (HER2) status.

They found that African-American women were more likely to have large tumors, more likely to have the aggressive triple-negative breast cancer and 40-70% more likely to be diagnosed at stage 4 of all subtypes of breast cancer. They were also 30-60% more likely to receive inappropriate treatment across all subtypes, except HR-/HER2+ breast cancer.

Fast facts about breast cancer
  • 232,340 American women were diagnosed with invasive breast cancer in 2013-14
  • There were 39,620 deaths from breast cancer in 2013-14
  • Breast cancer is the second most deadly cancer for women, after lung cancer.

Learn more about breast cancer

Hispanic white women were 30-40% more likely to be diagnosed at stage 2 and/or stage 3 across all breast cancer subtypes, and 20-40% more likely to receive inappropriate treatment (except HR+/HER2- and triple-negative cases).

In contrast, non-Hispanic white women were more likely to have smaller tumors, and the less-aggressive HR+/HER2- subtype of breast cancer.

The disparities continued across all stages of the disease. Compared with non-Hispanic whites, women of all other racial and ethnic groups were more likely to be diagnosed with more advanced stages of breast cancer, researchers found.

Asians and Pacific Islanders showed no disparity with non-Hispanic white patients in receiving appropriate treatment.

Disparities persisted after adjusting for insurance status, suggesting that other factors also play important roles.

In recent years, increased information about the molecular and genetic characteristics of breast cancer has helped improve treatment for the disease.

However, Chen comments:

"We found that there is a consistent pattern of late diagnosis and not receiving recommended treatment for some racial and ethnic groups across all breast cancer subtypes. The treatment for breast cancer is currently dependent on the type of breast cancer, defined by the estrogen receptor, progesterone receptor, and HER2 status. This is the reason why we think it's important to look at the disparities by subtype."

She adds that there is an opportunity to reduce the disparities and close the existing survival gaps between the different groups. By targeting specific groups, culturally appropriate interventions in breast cancer screening and care could be more effectively delivered for a better outcome.

Limitations of the study include the fact that 14% of the women in the original sample had to be excluded due to missing data, potential misclassification and variations in the data gathered by cancer registries.

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