The report from Dr. Steven Narod and colleagues recently published in JAMA1 and reviewed in this issue of The ASCO Post adds to the growing evidence regarding observed disparities in breast cancer outcomes by race and ethnicity among women in the United States. Since 1990, breast cancer death rates have dropped by 34%; nevertheless, survival disparities persist by race and ethnicity, with black women having the worst breast cancer survival.2 The biologic basis for poor outcome has long been suspected,3,4 although the contribution of socioeconomic factors can not be altogether disregarded.
Study Contributions
The contribution of this study, in my opinion, is twofold. First, the authors look at several racial and ethnic groups—not just white vs black. Comparing several groups, they show a similar trend that black women have the poorest breast cancer outcome.
Second, the authors focus on early-stage disease and show that even in women with tumors smaller than 2 cm, in whom outcomes are often excellent, disparities still exist by race and ethnicity. They found that although the 7-year actuarial breast cancer survival rate was well over 90% for women with stage I disease, the proportion of black women who died of their disease was approximately 9%, vs approximately 5% of white women and 3% of Asian women. Obviously, because of the short follow-up, the differences in outcome would be most apparent in the most aggressive tumors.
More Than Tumor Biology
To elucidate the potential reasons for this disparity, Narod and colleagues investigated the probability of tumors smaller than 2 cm presenting with features suggestive of aggressive behavior such as nodal involvement, distant metastasis, or triple-negative disease. Not surprisingly, the proportion of black women with these aggressive features was higher than in other races/
ethnicities.
However, for some of the aggressive categories, other racial/ethnic groups did not appear to be very far apart from black women. For instance, nodal involvement was 23.2% for South Asian vs 24.1% for black women. Still, this did not seem to significantly influence the outcome of South Asian women negatively, highlighting the complexity of this subject.
Although there is no question that tumor biology makes a huge contribution to the differences in breast cancer survival by race and ethnicity, many questions remain unanswered, and the authors acknowledged the limitations of their study. To address this issue fully, a transdisciplinary approach is needed. At a minimum, the biology of the tumor should be investigated using tissue samples5; further, the influence of comorbidities and adequacy of care should be investigated through chart reviews,6 and the influence of ancestry admixtures should be assessed.
Still, such an approach may only help explain disparities within a specific geographic location. However, breast cancer is a global disease. For one, there is still the question of whether the biology of breast cancer among black Americans is similar to that of black/African women all over the world. Additionally, the authors reported that Japanese American women have the lowest mortality from breast cancer and appear to develop more indolent types of breast cancer. Is this an influence of genetics or environment?
Screening and Clinical Trials
A couple of broader factors are also brought to light by the study. One pertains to screening7: If a tumor is already metastasized despite its small size, what would be the value of screening mammography? Should a different modality be used? Should the timing or frequency be changed? Should a risk-adapted approach be used, and if so, what should that approach be?
Another factor pertains to clinical trials. Racial and ethnic minorities, who have often been shown to have poorer outcomes, are the very patients who are underrepresented in clinical trials. I find that patients are quite willing to participate in these trials, but there are added burdens (eg, financial) and barriers (eg, language) to their participation. It is important to determine whether such a barrier is in place for every trial we design and to see how we can
mitigate it. ■
Disclosure: Dr. Royce reported no potential conflicts of interest.
References
1. Iqbal J, Ginsburg O, Rochon PA, et al: Differences in breast cancer stage at diagnosis and cancer-specific survival by race and ethnicity in the United States. JAMA 313:165-173, 2015.
2. DeSantis C, Ma J, Bryan L, Jemal A: Breast cancer statistics, 2013. CA Cancer J Clin 64:52-62, 2014.
3. Cunningham JE, Butler WM: Racial disparities in female breast cancer in South Carolina: Clinical evidence for a biological basis. Breast Cancer Res Treat 88:161-176, 2004.
4. Maskarinec G, Sen C, Koga K, Conroy SM: Ethnic differences in breast cancer survival: Status and determinants. Womens Health (Lond Engl) 7:677-687, 2011.
5. Middleton LP, Chen V, Perkins GH, et al: Histopathology of breast cancer among African-American women. Cancer 97(1 suppl):253-257, 2003.
6. Ademuyiwa FO, Gao F, Hao L, et al: US breast cancer mortality trends in young women according to race. Cancer. December 5, 2014 (early release online).
7. Amirikia KC, Mills P, Bush J, Newman LA: Higher population-based incidence rates of triple-negative breast cancer among young African-American women: Implications for breast cancer screening recommendations. Cancer 117:2747-2753, 2011.
Dr. Royce is Professor of Medicine and Director of the Multidisciplinary Breast Cancer Clinic and Program at the University of New Mexico Cancer Center in Albuquerque.
