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Specific Cell Actions May Help Explain Differences in Outcomes Between Black and White Women Diagnosed With Breast Cancer

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It’s been known for more than 20 years that Black women have worse survival rates than white women after a breast cancer diagnosis. Researchers have been trying to figure out why this is.

A study suggests that estrogen-receptor-positive breast cancer cells in Black women have a very strong survival mechanism, which may contribute to the worse survival rates.

The research was presented on April 18, 2015 at the 2015 American Association for Cancer Research Annual Meeting. Read the abstract of “The unfolded protein response may contribute to racial disparity in endocrine responsiveness in breast cancer.”

About 70% of breast cancers are estrogen-receptor-positive, which means their growth is fueled by the hormone estrogen. Treatments for estrogen-receptor-positive disease work by lowering the amount of estrogen in the body or blocking estrogen from attaching to the breast cancer cells. There are several types of hormonal therapy medicines, including:

  • aromatase inhibitors
  • selective estrogen receptor modulators (SERMs)
  • estrogen receptor downregulators (ERDs)

Tamoxifen, the generic name of Nolvadex, is the oldest and most prescribed SERM. Still, studies have found that about 50% of estrogen-receptor-positive breast cancers stop responding to tamoxifen. Doctors call this “treatment resistance.”

Black women diagnosed with estrogen-receptor-positive breast cancer treated with tamoxifen have worse overall survival and worse progression-free survival than white women diagnosed with estrogen-receptor-positive disease treated with tamoxifen.

Overall survival is how long a woman lives, whether or not the breast cancer grows. Progression-free survival is how long a woman lives without the cancer growing.

In this study, the researchers were looking for reasons why Black women diagnosed with estrogen-receptor-positive disease had worse outcomes than white women diagnosed with the same type of breast cancer.

They found that estrogen-receptor-positive breast cancers in Black women are less sensitive to tamoxifen. The reason these cancers are less susceptible to tamoxifen seems to be because the cancer cells activate what researchers call the “unfolded protein response.”

The unfolded protein response is a way cells respond to stress. When cancer cells are under stress from an anti-cancer treatment, such as tamoxifen, the unfolded protein response can be activated.

“[The unfolded protein response] can switch on a pro-survival pathway, allowing tumor cells to hunker down and wait out the attack,” said Ayesha Shajahan-Haq, Ph.D., oncology research assistant professor at Georgetown University and lead author of the study.

The researchers found that the unfolded protein response was more activated in estrogen-receptor-positive breast cancer cells in Black women compared to estrogen-receptor-positive breast cancer cells in white women. The researchers said this could lead to the cancer cells becoming resistant to tamoxifen.

So a more activated unfolded protein response could be part of the reason why Black women diagnosed with estrogen-receptor-positive breast cancer have worse outcomes than white women diagnosed with estrogen-receptor-positive disease.

The researchers said that other factors may be contributing to this difference, including access to regular mammograms, follow-up care, income level, and other social factors.

ALL women -- no matter their age, ethnicity, economic status, or other health conditions -- deserve the best breast cancer care and the best prognosis possible. While it may take time for researchers to develop a treatment that targets the unfolded protein response, social differences that affect prognosis should be eliminated.

Regular doctor visits and breast cancer screening is a good place to start. Breast cancer that is diagnosed early is typically easier to treat and offers the best survival chances. Regular screening for breast cancer, including annual mammograms and breast exams by a medical professional, is important for everyone. Paying for healthcare can be difficult, especially if you have limited income or are covered only by Medicare. But if you're older than 40, skipping regular mammograms is NOT an option. Stick with the screening plan you and your doctor decide is best for you. If scheduling problems or cost concerns are stopping you from getting a mammogram, talk to your doctor, a hospital social worker, or a staff member at a mammogram center. Ask about free mammogram programs and healthcare services in your area. It's YOUR health and YOUR future, and you deserve the best care possible.

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