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Race Gap in Survival Rates May Not Be Caused by Tumor Subtype

African-American women face worse survival rates than women of other races, overall

August 16, 2013

Written By Nicole Katze, MA, Writer and Editorial Coordinator
Reviewed By Kent Hoskins, MD

Research presented at the 2013 Annual Meeting of the American Association for Cancer Research found that African-American women have worse breast cancer-specific survival rates than women of other racial or ethnic groups, no matter the tumor subtype. Breast cancer-specific survival is the time from diagnosis to death from breast cancer.

This finding challenges the belief that more African-American women die from breast cancer because they are more likely than women of other races to be diagnosed with triple-negative tumors. These cancers tend to be sensitive to chemotherapy but do not respond to more recently approved targeted therapies such as hormonal therapy and trastuzumab (Herceptin).

This study has not yet been published in a medical journal. Until publication, its findings are considered preliminary.

Study Background 

Differences in survival rates between racial groups, particularly between African-American and Caucasian women, continue to be unexplained.

Participating researchers explored breast cancer survival by race and by tumor subtype to understand how survival is related to both factors.

Study Design

The investigators analyzed data on women enrolled in the Life After Cancer Epidemiology and Pathways studies.

Original researchers of both studies collected information from women living in Northern California and Utah who were diagnosed with breast cancer of all subtypes. Their goal was to draw conclusions about how women’s treatment, post-treatment lifestyle choices, and genetic backgrounds impact their quality of life and long-term survivorship.  

The 1,282 women selected for the current study were treated for one of the four subtypes of breast cancer identified using the PAM50 subtyping test. PAM50, a test available for use in the research setting, analyzes 50 different genes in tumor samples to determine the tumor’s subtype. The four subtypes respond to treatments differently and are associated with different outcomes, so knowing the subtype allows doctors to recommend the best treatment for each person.

  • Luminal A subtypes are hormone receptor-positive and HER2 negative
  • Luminal B subtypes are hormone receptor-positive and may also be HER2 positive
  • HER2 positive subtypes are HER2 positive, and either hormone receptor-negative or -positive
  • Triple-negative subtypes are HER2- and hormone receptor-negative. They are often basal-like, similar to the outer (basal) cells of the ducts of the breast. However, not all triple-negative breast cancers are basal-like

Luminal A and luminal B cancers tend to be more easily treated than HER2-enriched and basal-like, although luminal B cancers are usually more aggressive than luminal A.

All women identified their race through surveys completed by mail. Each woman’s subtype was determined by testing tumor samples.

Results

The women were followed for up to 15.5 years. At the median follow-up of 6.3 years:

  • 213 women died, 118 from breast cancer

Analysis of the women’s tumor subtypes and races showed:

  • Overall, African-American women were more likely to die from breast cancer than women of other races, no matter the tumor subtype
  • When analyzed by subtype, African-American women appeared to have a worse survival outcome for each subtype.  But given the relatively small number of deaths in each subtype group, these results are less certain from a statistical standpoint
  • Latina and Asian women were less likely to die from breast cancer than both African-American and Caucasian women
  • African-American women were more often diagnosed with basal-like or HER2-enriched breast cancer, and with luminal A or luminal B subtypes less often than Caucasian peers

What This Means for You

Although this study suggests African-American women have a greater risk of death from breast cancer than women of other races, know that your own experience with breast cancer will be unique. The information presented in this study represents a large group of women, not the experiences of any one woman.

Additional studies are needed to confirm the authors’ findings, which are limited in part due to the study’s shorter median follow-up time. Why differences in survival outcomes exist between racial groups continues to be a point of interest in cancer research. Though there are no concrete answers yet, the more scientists explore such differences the closer we come to an answer.

If you have questions about how race may influence your outcome, talk with your doctors. LBBC also offers information specific to African-American women on lbbc.org, as well as on triple-negative breast cancer, that you may find useful.

Kroenke, C, Kwan, M, Bernard, P, et al. Race and breast cancer prognosis by PAM50 subtype in the LACE and Pathways studies. Paper presented at: American Association for Cancer Research Annual Meeting; April 7, 2013. Washington, DC. 

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