Tumor biology predicts breast cancer treatment outcomes more than race
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Race did not significantly predict response to treatment outcomes among women with high-risk breast cancer, according to study results presented at San Antonio Breast Cancer Symposium.
Results showed tumor biology more strongly predicted pathologic complete response, EFS and other outcomes, an analysis of the I-SPY2 trial showed.
“We wanted to investigate whether there are disparities in breast cancer mortality in the context of the I-SPY 2 trial and how we can adjust to improve outcomes,” Laura J. Esserman, MD, MBA, director of the University of California, San Francisco. Breast Care Center and principal investigator of the I-SPY 2 trials, told Healio. “In our patient population in I-SPY 2, 12% are Black and we have great depth in our data, including the biology of each tumor. We have imaging and early endpoints and long-term follow up. All of this gives us power to investigate the critical issues that may underlie the differences in how patients respond to therapy and what we can do to improve outcomes.”
Black women are 40% more likely to die of breast cancer than white women, and pathologic complete response has been shown to be a significant predictor of distant RFS.
Investigators sought to assess whether racial disparities exist in achievement of pathologic complete response. They also examined the association between racial groups and 28 gene expression signatures linked to immune cell types, checkpoint inhibitor targets and immune signaling pathways.
The analysis of data from 907 patients (81% white; 12% Black; 7% Asian) from 10 treatment arms in the I-SPY2 trial.
Median follow-up was 4.4 years.
Results showed pathologic complete response rates did not differ significantly for Asian (OR = 1) or Black patients (OR = 0.89) compared with white patients.
“If a complete response to treatment is achieved, the outcome will be excellent and there is no difference among women of different races,” Esserman said. “However, if there is not a complete response, then outcomes are worse for Black women with hormone receptor-positive HER2-negative breast cancer.”
In addition, researchers observed no significant differences in EFS or residual cancer burden among Asian (HR = 1.1) or Black patients (HR = 1.37) compared with white patients.
The similar treatment outcomes among women of all races suggests tumor molecular subtype is a more significant factor in breast cancer survival than race, researchers concluded.
Researchers acknowledged study limitations, including the small number of self-reported Black and Asian patients and the fact the data did not capture socioeconomic differences that may have influenced treatment response.
“We have the ability to double the number of patients in this study, and the ability to look into more of the biology that may underlie the differences in outcome in the hormone receptor-positive, HER2-negative subtype among Black women,” Esserman said.
Black women who received appropriate therapies based on their tumor profiles saw the same benefits of treatment as white women.
This highlights the importance of expanding access to innovation to address breast cancer disparities, Olufunmilayo Olopade, MD, FACCR, Walter L. Palmer distinguished service professor of medicine and human genetics and director of Center for Clinical Cancer Genetics and Global Health at The University of Chicago Medicine, told Healio.
“The study highlights the need to broaden access to molecular diagnostic tests by expanding access in low-resource settings, and oncologists need to adopt risk stratifications using the modern tools of precision oncology,” Olopade said. “We have funding from the NCI and now plan to apply for a Breast Cancer Disparities SPORE focused on closing the mortality gap in breast cancer by providing career enhancement opportunities for young investigators — such as the study’s lead author Beverly Kyalwazi, BS — and address the best science questions using I-SPY and other distributed networks to develop innovative research aimed at gaining a better understanding of the biologic basis of health disparities in diverse populations with the intent of promoting equity by removing systemic barriers.”
Perspective
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Theresa Shao, MD
Advances in breast cancer treatment have dramatically reduced breast cancer mortality, but Black women still are more likely to die of breast cancer than those of any other racial or ethnic group. This study, which examined neoadjuvant treatment for patients with breast cancer, showed that biology rather than race is a more significant factor for predicting response to treatment. The fact that treatment outcome is more likely to be associated with tumor biology than race will allow us to focus more on strategies to ensure equal access to care among Black women, and additional research in this area hopefully will decrease the mortality rate among Black women in the future.
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Kyalwazi B, et al. Abstract GS4-02. Presented at: San Antonio Breast Cancer Symposium; Dec. 7-10, 2021; San Antonio.
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