Recent challenges to the traditional recommendations that American women initiate annual screening mammography at age 40 years have the potential for exerting a disproportionately adverse effect on African American women because of the well-documented younger age distribution for breast cancer in this population subset. Early detection of breast cancer is the most powerful determinant of outcome, and this will be particularly relevant for tumors expressing phenotypes that cannot be controlled with targeted agents such as endocrine therapy and/or trastuzamab. African American women have higher mortality rates from breast cancer, and this is at least partially explained by the fact that they tend to present with more advanced stages compared to White American women. They therefore represent a community that has been the focus of many breast cancer awareness and screening/early detection programs. Our study provides further evidence of the need to continue intensive breast cancer surveillance among African American women age 40–49 years. By studying data from the California Cancer Registry, we found higher population-based incidence rates of locally-advanced breast cancer and triple-negative breast cancer among African American women.
Although the lifetime incidence rates of breast cancer are higher for White American compared to African American women, the Surveillance, Epidemiology and End Results (SEER) Program documents that for women younger than age 45 years, population-based incidence rates are higher for African Americans(13
). Several investigators have demonstrated that the frequency of TNBC is higher for African American compared to White American breast cancer patients (14
). Carey et al (18
) furthermore demonstrated that the risk of triple-negative breast cancer is particularly high among premenopausal African American women, based upon analysis of the Carolina Breast Cancer Study. By reporting on age- and race/ethnicity- specific patterns of disease in the California Cancer Registry, our study provides powerful population-based evidence regarding the importance of aggressive screening for early detection of breast cancer in young African American women.
As background for the updated screening guidelines presented by the U.S. Preventive Services Task Force (USPSTF) in November 2009(5
) reviews of the data from the historic mammography screening trials were prepared by Nelson et al(19
) and Mandelblatt et al on behalf of the Cancer Intervention and Surveillance Modeling Network (CISNET)(20
). In summary, they found that for women age 40–49 years, approximately 1900 must be invited to mammographic screening in order to save one life; for women age 50–59 years, approximately 1300 must be invited; and for women age 60–69 years, approximately 400 must be invited. They also found that initiation of mammography screening at age 40 rather than age 50 years results in an average gain of 33 life years per 1000 women screened. CISNET therefore stated: “If the goal of a national screening program is to reduce mortality in the most efficient manner, then programs that screen biennially from age 50 years…are among the most efficient on the basis of the ratio of benefits to the number of screening mammograms. If the goal of a screening program is to efficiently maximize the number of life-years gained, then the preferred strategy would be to screen biennially starting at age 40 years.”(20
) The USPSTF opted to advocate in favor of supporting an efficiency-based screening model rather than a longevity-based program, and they therefore issued the statement that “The USPSTF recommends against routine screening mammography in women aged 40–49 years… The USPSTF recommends biennial screening mammography for women between the ages of 50 and 74 years.”(5
) CISNET furthermore commented that none of the mammography screening models were likely to capture differences in outcome among specific population subsets such as “black women who seem to have more disease at younger ages than white women”(20
). The USPSTF recommendation statement did not comment on the potential impact of their screening recommendations on race-ethnicity-associated breast cancer disparities.
Our study serves to inform the discussion regarding relevance of mammography screening for African American women age 40–49 years. We found more advanced stage of disease at diagnosis in these younger African American women, and we also found higher incidence rates of TNBC for this population subset. Since mammography screening programs should improve early detection rates for breast cancer, and since early detection of TNBC is critical for improving its successful treatment, we believe that our study findings provide compelling evidence that screening mammography should be particularly important for young African American women. The USPSTF recommendation that routine screening mammography should not be initiated until age 50 years has the potential for widening the magnitude of breast cancer outcome disparities between African American and White American women.
The CCR data on race/ethnicity-associated frequency of TNBC is consistent with other studies, as shown in . The population-based incidence rates featured in our study serve to strengthen the validity of these observations. These rates indicate an inherently higher risk of TNBC for NHB/African American women, refuting the argument that the larger proportion of TNBC in African American women is an artifact of the “denominator” phenomenon (i.e. African American women appear to have more TNBC simply because they have fewer total breast cancers compared to White American women). Our data on women from California demonstrate increased population-based risk of TNBC for NHB women.
Published studies of ER-negative/PR-negative/HER2/neu-negative (TNBC) requency by race/ethnic identity.
Our study is limited by our unfortunate inability to correlate mammography screening information with the age- and race/ethnicity-specific breast cancer incidence rates. However data from the California Health Interview Survey (CHIS) indicate similar mammography utilization rates for African American and White American women, but somewhat lower rates for Hispanic/Latina women (unpublished data) and this finding mirrors national data on mammography utilization reported by the American Cancer Society(1
). Although the data regarding effectiveness of mammography in detecting TNBC (compared to detection rates for non-TNBC) are limited, the available published studies indicate that frequency of mammographically-occult breast tumors is similar for TNBC and non-TNBC. TNBC does however, appear to be less-frequently associated with microcalcifications and is more likely to be identified as a mass or asymmetric density(21
). Furthermore, Ma et al demonstrated that mammographic density (a common imaging finding among premenopausal women) is a risk factor for TNBC as well as for non-TNBC(25
Another notable limitation of our study is the fact that the CCR (similar to the SEER Program) lacks detailed information on menstrual history and reproductive factors. Millikan et al(26
) and other investigators(27
) have suggested that childbearing patterns and lactation history may account for race/ethnicity-associated variation in breast cancer burden. Others have been unable to confirm these hypotheses (28
). Yet other investigators have reported elevated risk of TNBC among contemporary female populations of continental Africa(29
), suggesting that African ancestry may be associated with some heritable risk factor for TNBC(32
). Our population-based California dataset is unable to address any of these issues.
In summary, our data from California (which appears to be representative of national data) demonstrates increased risk of advanced-stage breast cancer and triple-negative breast cancer in African American women compared to White American and Hispanic American women. These patterns are notably prominent for women younger than age fifty, suggesting that mammography screening to improve early detection of biologically-aggressive patterns of breast cancer will be particularly relevant for younger African American women, especially since overall breast cancer incidence rates are higher for African American women in the premenopausal age range.