Black patients with triple-negative breast cancer may receive immunotherapy at lower rates than White patients, according to new findings presented by Freeman et al at the 2024 American Association for Cancer Research (AACR) Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved (Abstract C035).
Background
Black women may be disproportionately affected by triple-negative breast cancer, an aggressive subtype of breast cancer characterized by the lack of three cell surface receptors. The absence of these receptors makes patients with triple-negative breast cancer ineligible for many of the molecularly targeted therapies used to treat other breast cancer subtypes.
“The lack of a treatment specifically tailored to the biology of [triple-negative breast cancer], coupled with its typically more aggressive growth, makes [triple-negative breast cancer] particularly challenging to treat, resulting in worse outcomes,” explained senior study author Frederick M. Howard, MD, Assistant Professor at the University of Chicago.
Immunotherapy has recently become available for the treatment of triple-negative breast cancer, demonstrating positive clinical trial results that have led to the U.S. Food and Drug Administration (FDA) approval of the immunotherapy agent pembrolizumab alongside chemotherapy in patients with PD-L1–positive, metastatic triple-negative breast cancer in 2020 as well as in patients with high-risk, early-stage triple-negative breast cancer in 2021. Another immunotherapy agent, atezolizumab, initially received accelerated approval from the FDA to treat patients with advanced PD-L1–positive triple-negative breast cancer in 2019, but the approval was withdrawn in 2021.
“Since 2019, immunotherapy has become a standard treatment option for [triple-negative breast cancer], but it is mostly unknown whether there are racial/ethnic disparities in who receives immunotherapy or in the outcomes for early-stage and metastatic [triple-negative breast cancer],” emphasized lead study author Jincong Q. Freeman, MPH, a PhD candidate at the University of Chicago. “Understanding these elements is key to developing strategies or interventions to ensure equitable access to immunotherapy and to mitigate the known racial/ethnic disparities in [triple-negative breast cancer] outcomes.”
Study Methods and Results
In the new study, investigators used data from the National Cancer Database to examine the trends and demographic factors associated with the receipt of immunotherapy among over 10,000 patients with triple-negative breast cancer.
Between 2017 and 2021, the proportion of patients who received immunotherapy increased from 4.2% to 48.0% among those with early-stage triple-negative breast cancer and from 5.3% to 33.1% among those with metastatic triple-negative breast cancer.
The investigators discovered that among the patients with early-stage triple-negative breast cancer who underwent neoadjuvant chemotherapy in 2021, 45.9% of Black patients and 48.2% of White patients received immunotherapy. This translated to an 11% lower rate of immunotherapy receipt in Black patients after adjusting for clinical factors. However, the difference was no longer statistically significant once the investigators further accounted for socioeconomic differences between the populations. They suggested that socioeconomic factors might be one of the main barriers to immunotherapy access among Black patients with early-stage triple-negative breast cancer, but acknowledged that the data represented an early snapshot—since immunotherapy for early-stage triple-negative breast cancer was not approved until the middle of 2021.
Among the patients with metastatic triple-negative breast cancer who underwent chemotherapy between 2019 and 2021, 28.1% of Black patients and 35.5% of White patients received immunotherapy. After adjusting for clinical and socioeconomic factors, Black patients were found to be 37% less likely to receive immunotherapy compared with White patients, a statistically significant difference.
Additionally, the researchers found that the pathologic complete response and overall survival rates were comparable between Black and White patients with early-stage triple-negative breast cancer and metastatic triple-negative breast cancer who received immunotherapy, respectively.
“A key finding of our study is that Black patients with metastatic [triple-negative breast cancer] were less likely than White patients to have received immunotherapy, but when they did receive immunotherapy, they had a similar overall survival rate as White patients. This tells us that receiving immunotherapy may help mitigate racial differences in the survival of patients with metastatic [triple-negative breast cancer],” Mr. Freeman highlighted.
Factors found to be associated with a lower likelihood of immunotherapy receipt in patients with triple-negative breast cancer were Medicare enrollment and comprehensive community program–based care. For instance, those who were enrolled in Medicare had a 16% lower likelihood of receiving immunotherapy compared with those who had private insurance and patients who received care through a comprehensive community program had a 20% to 21% lower likelihood of receiving the treatment compared with those at academic/research centers.
Conclusions
Since PD-L1 expression is a prerequisite for pembrolizumab in patients with metastatic triple-negative breast cancer, additional research may be needed to understand whether there are differences in tumor PD-L1 expression between Black and White patients that could contribute to the observed disparities in immunotherapy receipt.
Limitations of the study included its retrospective design, the lack of information in the National Cancer Database about the immunotherapy regimens patients received, and the lack of information about PD-L1 tumor expression in different populations.
“Expanding insurance coverage, lowering health-care costs, and improving treatment distribution and access—particularly for those programs serving socioeconomically disadvantaged communities—are needed to move toward equitable access to immunotherapy across different populations with [triple-negative breast cancer],” concluded Mr. Freeman.
Disclosure: The research in this study was supported by the Agency for Healthcare Research and Quality, the Breast Cancer Research Foundation, the U.S. Department of Defense, the National Institutes of Health, the Cancer Research Foundation, the Lynn Sage Breast Cancer Foundation, and the Susan G. Komen Breast Cancer Foundation. For full disclosures of the study authors, visit aacrjournals.org.
