Introduction
Across the world, breast cancer is the most common malignancy diagnosed in women under 40 years of age [
1,
2]. A number of studies have demonstrated that women under 40 years with breast cancer have significantly worse outcomes compared to older women. Breast cancers in young women are typically more biologically aggressive, diagnosed at a later stage, and are more likely to recur [
3]. As the rate of early onset breast cancer is increasing [
4] understanding this difference in outcomes is of great clinical importance. As is the case with other health measures, breast cancer incidence is impacted by race. While White women have the highest incidence of breast cancer across most age groups, in women under 35 years, Black women are significantly more likely to be diagnosed with breast cancer compared to other racial and ethnic groups [
5,
6].
Not only are there differences in the incidence of breast cancer by race/ethnicity, there are consistent disparities in outcomes [
7]. Minority groups—including Blacks, Hispanics, Asian Americans, and American Indians—are more likely to be diagnosed at an advanced stage as compared to Whites [
5]. In comparison to all other racial/ethnic groups, Black women have the highest percentage of stage III or IV tumors at time of diagnosis [
4]. Specifically with regards to triple negative breast cancer (TNBC), which is more prevalent in Black than White women, both five- and ten-year survivals are worse in Black women compared to White women [
8‐
10]. Disparities in breast cancer outcomes by race/ethnicity are well established both nationally and within the city of Chicago [
7,
11‐
13].
There are a paucity of data examining the potential synergistic effects of age and race on breast cancer outcomes. Specifically, data comparing responses to neoadjuvant chemotherapy (NACT) by race and age groups are lacking [
14‐
16]. As the ability to achieve a pathological complete response (pCR) after NACT is generally associated with improved long-term outcome, evaluating pCR rates by age
and race could provide valuable insights into mechanisms underlying cancer health disparities [
14,
16‐
18]. Given the well-documented racial/ethnic disparities observed, along with the increasing incidence of breast cancer in women under 40—which disproportionately affects Black women—it is important to more specifically characterize breast cancer patterns and outcomes in young Black women.
In this study, we analyzed the outcomes of young Black and young White women with breast cancer treated at the University of Chicago, comparing them to each other as well as to corresponding groups of older Black and older White women. While there has not been a uniform consensus in the literature as to the specific age cutoff which defines a “young woman with breast cancer,” many studies use the age of 40 [
18,
19]. As Black women and young women have poorer outcomes compared to White women and older women, we hypothesized that Black women diagnosed with breast cancer under age 40 years would have lower pCR rates and worse long-term outcomes when compared to young White women as well as older White and Black women.
Discussion
These data reinforce the importance of focusing attention and resources on the management of young Black women with breast cancer. In our cohort, young Black women did not respond as well to NACT as their young White counterparts, had a higher risk of recurrence, and a poorer DFS; this disparity in outcome persisted, even when adjusting for grade, stage, and breast cancer subtype. We also found that young Black women who did not have a pCR tended to fare worse than young White women who did not have a pCR, and work to identify the root causes of this difference in outcomes is ongoing. Breast cancer patients who participated in clinical trials had better long-term outcomes, and Black women in our cohort had lower rates of participation in therapeutic clinical trials. While it is possible that participation in trials of novel agents lead to improved outcomes, it is more likely that trial enrollment served as a surrogate for social determinants of health, which have previously been shown to correlate with improved outcomes after a diagnosis of breast cancer [
23].
It has been established that there are racial differences in engagement in screening mammography. Black women are screened less frequently than White women for a number of reasons, including limited access to care [
24,
25]. Interestingly, we did not see significant differences in tumor size, nodal status, or stage at presentation in our older patients, regardless of race. In our younger population, we did observe that our young Black patients were more likely to present with higher stage disease than our young White patients, and as these women are under 40 years, this difference is unlikely to be related to differences in screening. Possibilities for this difference could be due to differences in tumor biology (Black women are more likely to have TNBC, which is faster growing and more likely to present with nodal involvement), access to care, decreased awareness of cancer risk, delay in referral to cancer providers, and/or distrust of the medical system.
However, as access to genetic testing becomes more available and screening MRIs are more frequently performed in those at increased risk, it becomes even more important to consider inequities in screening in younger women. Disparities in screening in younger women are likely to play a greater role in timing of presentation, stage at diagnosis, and eventual outcomes of women under 40 in the future.
Adherence to hormonal therapy, chemotherapy, and/or radiation may also differ based on race and age, and could in part have contributed to the disparities observed within our cohort. Across all ages, Black women more frequently report nonadherence to endocrine therapy due to increased side effects, inability to pay for therapy, and incomplete understanding of recurrence risk [
26,
27]. It has also been shown that Black women are less likely to complete a full chemotherapy regimen compared to their White counterparts [
28,
29]. As a whole, underserved populations are more likely to state barriers to adhering to therapy, and these issues likely contribute to the disparities in outcomes between Black and White patients, regardless of age.
Another important factor to consider is delay between diagnosis and treatment initiation. The young Black women in our cohort were more likely to have a larger gap between diagnosis and initiation of NACT than young White women; mean gap from diagnosis to treatment start was 41 days in young Black women compared to 33 days in young White women (
p = 0.004). A preliminary investigation into the reason for such delays included psychosocial factors such as insurance issues, psychiatric illness management, and relocation for treatment. Studies have shown that patients who have longer delays in treatment, for example a greater than 8 week period between diagnosis and initiation of NACT, are less likely to achieve a pCR compared to patients without such delays [
30,
31]. Rather than the delays themselves causing disparities in outcomes, it is likely that these delays serve as a surrogate marker for the underlying social determinants of health that are truly driving these differences in outcomes.
Work is ongoing to further elucidate the underlying etiology of the disparities seen in our University of Chicago cohort, with a focus on young Black women. A more comprehensive and detailed investigation is warranted in an effort to improve response and survival in this population of young women. In the meantime, it is critical to increase awareness of the poor outcomes observed in this group of particularly vulnerable women.
This study is not without its limitations. As an academic, single-center study, there is a limit to the generalizability of the results. In addition, there was a relatively small number of women receiving neoadjuvant chemotherapy, at just 397 women within the age and race parameters of this study. This translated to a low sample size when looking at pCR rates, particularly when further broken down by breast cancer subtype. A more robust analysis in a larger sample of women from multiple centers is needed to further validate these findings.
Future work will investigate the biological and social factors underlying the disparities identified in this cohort study, focusing on social determinants of health, which are likely driving the poor outcomes among young Black women. Only with a better understanding of the factors driving poor outcomes among young Black women with breast cancer can we even begin to eradicate the disparities in our most vulnerable breast cancer population.
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