Philadelphia, October 6, 2021—A new study by health equity researchers in the ECOG-ACRIN Cancer Research Group sheds light on the impact of chronic stress on women with breast cancer. The study shows that a high allostatic load was associated with a lower likelihood of completing chemotherapy and a lower overall survival rate in a group of patients with lymph node-positive or high-risk lymph node-negative HER2-negative breast cancer. The results are part of the 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved, occurring online October 6-8, 2021.
Allostatic load is the “wear and tear” on the body caused by lifelong exposure to stressors such as social isolation, poverty, and racism, which are common among racial/ethnic minorities. An elevated allostatic load can lead to various health problems, such as high blood pressure, increased body mass index, kidney disease, inflammation, arthritis, and other conditions.
“We observed that women with breast cancer who had a high allostatic load at the beginning of the study had a greater likelihood of stopping chemotherapy early and a higher risk of death,” said presenter Samilia Obeng–Gyasi, MD, MPH, a surgical oncologist at The Ohio State University Comprehensive Cancer Center. “In contrast, we did not observe an association between genetic ancestry and survival or chemotherapy completion. This finding suggests that allostatic load may be better than genetic ancestry at predicting chemotherapy completion and overall survival.”
Prior studies suggested that allostatic load and genetic ancestry each play a role in poor breast cancer outcomes. However, this is the first study to look at both factors at the same time in a study population.
The researchers analyzed data from the E5103 phase III clinical trial, one of the first large breast cancer treatment trials to assemble a biorepository and database of patient information for future research, including demographics and DNA (Miller KD. J Clin Oncol 2018). Patients in the trial had lymph node-positive or high-risk lymph node-negative, HER2-negative breast cancer.
Using genomic analyses and other patient information from the E5103 repository, Obeng-Gyasi and colleagues examined chronic stress, measured by allostatic load, across three broad categories of genetic ancestry—African, European, and other. Among the 348 patients included in the analysis, approximately 80 percent had European ancestry, 10 percent had African ancestry, and 10 percent had another ancestry.
“Patient behavior and clinical outcomes cannot be isolated from the effects of their social environment,” said Dr. Obeng–Gyasi. “Allostatic load provides us with a way to evaluate the effects of social and environmental stressors on a patient’s physiology.”
Allostatic load was measured in patients in E5103 using biomarkers of the cardiovascular, immune, and metabolic systems collected before starting treatment. Examples of the biomarkers included body-mass index, blood pressure, creatinine, and several cytokines.
After adjusting for genetic ancestry, the researchers found that each 1 unit increase in allostatic load score was associated with a 15 percent reduction in the likelihood of completing chemotherapy and a 14 percent increase in the risk of death.
“These results suggest that long-term exposure to chronic social and environmental stress may contribute to poor outcomes in patients with breast cancer,” said Dr. Obeng-Gyasi.
She explained that with further research, measuring allostatic load may be a useful tool to predict which patients with breast cancer may be at increased risk for stopping chemotherapy early or having poor survival. “Future prospective clinical trials with repeated measures of allostatic load may provide greater insight into its relationship to treatment and survival, especially if allostatic load is collected multiple times during the active treatment and survivorship phases of care,” she added.
A limitation of the study is that the analyses included only a subpopulation of patients with breast cancer; therefore, the results may not apply to all patients. An additional limitation is the small sample size.
The ECOG-ACRIN Cancer Research Group sponsored this study with support from the National Cancer Institute, part of the National Institutes of Health.
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