Household income linked to recurrence score, mortality in ER-positive breast cancer
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Key takeaways:
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Women with breast cancer in low-income households had higher recurrence scores and worse OS
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Further study is needed to identify potential drivers of the association
Low household income appeared independently associated with higher 21-gene recurrence scores and significantly worse survival outcomes among women with ER-positive breast cancer, according to data published in JAMA Network Open.
“We have known that income level increases the incidence of poor-prognosis triple-negative breast cancer, but our new study presents the first data to show that income level impacts survival even in breast cancer with a better prognosis,” Anurag K. Singh, MD, director of radiation research and professor of oncology and Roswell Park Comprehensive Cancer Center, told Healio. “Based on these findings, we are excited to institute financial counseling for breast patients, as well.”
Background and methodology
Prior research has shown associations of low income and higher incidence of triple-negative breast cancer. Singh and colleagues sought to examine associations of household income with 21-gene recurrence score and OS among women with ER-positive breast cancer.
The cohort study included 119,478 women (median age, 60 years; interquartile range, 52-67) diagnosed with ER-positive, pT1-3N0-1aM0 breast cancer between 2010 and 2018. Among the women, 82.2% identified as non-Hispanic white, 7.7% as Black, 6.1% as Hispanic and 4% as Asian/Pacific Islander. All had received surgery and adjuvant endocrine therapy with or without chemotherapy.
Researchers defined high and low neighborhood-level household income levels as above or below the median household income of $50,353, based on each patient’s ZIP code. About two-thirds (68.8%) of the study participants reported a household income above the median, while 31.2% reported an income below the threshold.
Recurrence score and OS served as the primary endpoints. Recurrence score ranged from 0 to 100 based on gene expression signatures indicating the risk for distant metastasis, with scores of 25 or below indicating non-high risk and scores of 26 or higher indicating high risk.
Results
Logistic multivariable analysis revealed an association of low vs. high income with a higher recurrence score (adjusted OR = 1.11; 95% CI, 1.06-1.16). Low income also appeared associated with worse OS (adjusted HR = 1.18; 95% CI, 1.11-1.25).
Researchers identified a statistically significant interaction between levels of income and recurrence score (P < .001 for interaction).
Subgroup analysis showed significant findings among women with recurrence scores below 26 (adjusted HR = 1.21; 95% CI, 1.13-1.29), but no significant survival difference between incomes level for those with recurrence scores of 26 or higher (adjusted HR = 1.08; 95% CI, 0.96-1.22).
Study limitations include unavailability of certain clinically relevant variables, such as performance status and tumor recurrence, and lack of patient-level income data.
Next steps
Further study is needed to identify the mechanism behind the association of socioeconomic determinants of health and intrinsic tumor biology, researchers wrote.
“This study shows that income can significantly change the basic biology and treatment responsiveness of breast cancer,” Singh told Healio. “Next steps will be to develop possible biomarkers and better questionnaires to address the manifold impacts of low income ... our work also has implications for clinical trial design. Future studies should consider using income or financial toxicity as a stratifying variable.”
For more information:
Anurag K. Singh, MD, can be reached at anurag.singh@roswellpark.org.
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Ma SJ, et al. JAMA Netw Open. 2023;doi:10.1001/jamanetworkopen.2023.0179.
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