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 some of the survival differences between black and white women with breast cancer may be because black women are more likely to be diagnosed with triple-negative breast cancer and are also more likely to stop hormonal therapy early.
The study was published online on May 11, 2015 by the Journal of Clinical Oncology. Read the abstract of “Racial and Ethnic Differences in Breast Cancer Survival: Mediating Effect of Tumor Characteristics and Sociodemographic and Treatment Factors.”
In this study, the researchers looked at the records of 17,268 women who were diagnosed with stage I, stage II, or stage III (early-stage) breast cancer between January 2000 and December 2007:
- 533 women were Asian
- 1,122 women were Hispanic
- 1,345 women were black
- 14,268 women were white
The researchers classified the cancers into four subtypes:
- luminal A breast cancer: estrogen-receptor-positive and/or progesterone-receptor-positive, HER2-negative, and low or intermediate tumor grade
- luminal B breast cancer: estrogen-receptor-positive and/or progesterone-receptor-positive, and either HER2-positive and any tumor grade or HER2-negative and high tumor grade
- HER2 type breast cancer: estrogen-receptor-negative, progesterone-receptor-negative, HER2-positive, and any tumor grade
- triple-negative breast cancer: estrogen-receptor-negative, progesterone-receptor-negative, HER2-negative, and any tumor grade
Tumor grade is a way to describe how different the cancer cells’ appearance and growth patterns are from healthy cells. Low grade tumors have cells that look a little different from healthy cells and grow in organized patterns. Intermediate grade tumors have cells that don’t look like healthy cells and are growing and dividing a little faster than normal. High grade tumors have cells that look very different from healthy cells and are growing in disorganized, irregular patterns.
They then looked to see if there were any links between the women’s ethnicity, the subtype of cancer they were diagnosed with, and other factors, including survival, age at diagnosis, stage at diagnosis, and body mass index (BMI) at diagnosis in the approximately 6 years of follow-up.
- The average age at diagnosis was youngest in Asians (51.1 years) and Hispanics (52 years).
- Black women were more likely to be diagnosed with:
- stage III disease (24%)
- high tumor grade (64.6%)
- triple-negative disease (29.6%)
- White women were more likely to be diagnosed with:
- stage I disease (45.6%)
- estrogen-receptor-positive disease (76.1%)
- Asian and white women were more likely to be diagnosed with the luminal A subtype (48% and 47.4%, respectively)
- Black women had the highest BMI (31.5) at diagnosis. A BMI higher than 25 is considered overweight.
- Overall, black women were 21% more likely to die from breast cancer compared to women of other ethnicities.
- Asian and Hispanic women were less likely to die from breast cancer compared to white women.
- For black and white women diagnosed with luminal A breast cancer, black women were 77% more likely to die from breast cancer compared to white women.
- For black and white women diagnosed with luminal B breast cancer, black women were 56% more likely to die compared to white women.
- For women diagnosed with estrogen-receptor-positive breast cancer, the survival differences between black and white women were greatest in the first 2 years after diagnosis.
- There were no survival differences by ethnicity for women diagnosed with triple-negative breast cancer or HER2-type breast cancer.
The results of this study add further documentation to differences in outcomes for black and white women diagnosed with breast cancer and also offer some new insights.
Black women were more likely to be diagnosed with breast cancer subtypes that have a worse prognosis. Still, the researchers found the greatest difference in survival was in the 2 years after diagnosis between black and white women who were diagnosed with hormone-receptor-positive disease and had almost the exact same treatments.
The researchers aren’t sure why this is. It could be because black women waited longer to start treatment than white women. It could also be that the process of being diagnosed took longer for black women, which would mean they would start treatment later. It also could be because black women are more likely than white women to stop hormonal therapy early and so don’t finish the whole 5- or 10-year course of treatment.
More research is needed to fully understand why the survival differences are so great in the first 2 years after diagnosis for black and white women diagnosed with hormone-receptor-positive disease.
ALL women -- no matter their age, ethnicity, economic status, or other health conditions -- deserve the best breast cancer care and the best prognosis possible. Any 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.