This is the first installment of a five-part monthly series that will discuss the pathologic, genomic, and clinical factors that contribute to the racial survival disparity in breast cancer. The series, which is adapted from an article that originally appeared in CA: A Cancer Journal for Clinicians,1 a journal of the American Cancer Society, will also review exciting and innovative interventions to close this survival gap. This month’s column reviews the scope of this important health care issue.
The National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results Program (SEER) has estimated that 231,840 new cases of female breast cancer will be diagnosed in 2015, representing 14% of all new cancer cases among women. The NCI also has estimated 40,290 deaths from breast cancer, representing 6.8% of all cancer deaths among women.2 Breast cancer is the second leading cause of cancer death among women after lung cancer. It is well known that there has historically been a significant racial divide in breast cancer incidence (rate of new occurrences of breast cancer) and mortality (death) rates. Caucasian women were more likely to be diagnosed with breast cancer, but African American women were more likely to die from it.
However, in a recently released study by DeSantis et al. this incidence trend no longer holds, and in 2012 there was a convergence of breast cancer incidence rates at 135 cases per 100,000 women for both Caucasian and African American women.3 In addition, this recent analysis revealed that the mortality disparity between African American and Caucasian women has continued to increase, with a death rate 42% higher in African American than in Caucasian women in 2012. While overall improvements in therapy have led to a decrease in breast cancer death rates in the United States since 1990, the decreases in death rates began earlier and have been larger in proportionate terms for Caucasians than for African Americans.4,5 According to SEER data from 1975 to 2011, Caucasian women had a 23% increase in breast cancer incidence and a 34% decrease in mortality, whereas African American women experienced a 35% increase in incidence and a 2% increase in mortality.6
Beyond national statistics and on a more-local level, several studies have explored regional variations in breast cancer mortality by race. One such study analyzed mortality data from the National Center for Health Statistics from 1975 to 2004.5 The researchers discovered that trends in breast cancer death rates varied widely by region. While breast cancer death rates in Caucasian women decreased in all 50 states, among African American women in 37 states analyzed, breast cancer death rates increased in 2 states, were level in 24 states, and decreased in only 11 states. Many of the states in which African American breast cancer death rates were level or rising were in the South and Midwest.
There are also differences in age and stage at diagnosis between African American and Caucasian women. Although the overall incidence of breast cancer has been historically higher in Caucasians, the incidence profile changes when the data are looked at by age. Among African American women with breast cancer, 33% are diagnosed at an age younger than 50 years, compared with 21.9% among Caucasian women.7
In women younger than 35 years, the incidence of breast cancer in African Americans is 1.4-2.0 times that of Caucasians.8 In addition, African American women present with more advanced-stage disease. Again, using the SEER program and examining data from 2005-2011, 62% of Caucasians had localized disease (cancer confined to the breast and potentially curable) versus 53% of African Americans. In all, 5% of Caucasians had distant disease (cancer outside the breast and treatable but not curable), compared with 9% of African Americans.9 A recent study in JAMA of 373,563 women with breast cancer during 2004-2011 found that African American women were less likely to be diagnosed with stage I breast cancer than were non-Hispanic white women across all age groups (non-Hispanic white women, 50.8%; African American women, 37.0%).10
The researchers examined further those women with small breast cancers (breast tumors ≤ 2 cm) and the percentages of nodal metastases (cancer in the lymph nodes) and distant metastases (cancer outside the breast) by race/ethnicity. The authors found that an African American woman with a small-sized breast tumor was more likely to present with lymph node metastases and distant metastases. Significantly, African American women were also more likely to die of breast cancer with small-sized tumors than were non-Hispanic white women.