Researchers found African American women with estrogen-receptor positive (ER+) breast cancer generally had poorer outcomes than European Americans.
The research team believes the disparity is related to survival mechanism within the cancer cells, Georgetown University Medical Center reported. Breast tumors in African American women proved to be more resistant to tamoxifen, a leading cancer treatment that increases the activation of the "unfolded protein response" (UPR). If UPI is activated within a cancer cell due to cancer treatment it can switch on a pro-survival pathway that keeps the cancer alive.
"From our gene analyses, we found increased activation of the UPR pro-survival pathway in African-American patients, compared with other patients, along with increased activity of a number of genes associated with that pathway," said the study's lead investigator, Ayesha Shajahan-Haq, an oncology research assistant professor. "This can lead to increased resistance to common therapies."
About 70 percent of all breast cancers are ER+, meaning they need estrogen to grow. These types of tumors are treated by preventing estrogen from reaching them, but about 50 percent of treated tumors develop resistance. African-American women with this breast cancer subtype were found to have worse progression-free and overall survival than European American women who received the same treatment.
"Our findings offer a partial understanding of racial differences within ER+ breast cancers. We demonstrate both increased resistance to anti-cancer therapy in African-American patients as well as the reason that resistance occurs," Shajahan-Haq said. "Biology may not be the only factor contributing to the racial disparities in outcome in the general public. Factors such as access to mammography, follow-up care or treatment, income status and other social factors have also been shown to contribute to disparities in outcome."
The researchers believe drugs that target the critical pro-survival UPR pathway could help reduce treatment resistance, which could help improve the outcomes of African American women with thus subtype of breast cancer.
The findings were presented at the American Association for Cancer Research (AACR) Annual Meeting 2015.
