Abstract C037: Diurnal cortisol profiles of Chinese American breast cancer survivors

Abstract Purpose Chinese American breast cancer survivors (CABCS) are an underserved and understudied population with unique sociocultural stressors. Cortisol, a key hormone of the HPA axis and biomarker of stress, can be dysregulated by cancer-related distress. We aimed to characterize diurnal cortisol rhythms in CABCS, as no prior studies have examined their cortisol patterns. Methods We analyzed data from Chinese American women (N = 167) with stage 0–III breast cancer who completed primary treatment within the past 36 months. Participants collected salivary cortisol samples at four time points (∼20 minutes after waking, noon, 5 PM, and 9 PM) across two consecutive days. Cortisol was assayed, and summary metrics were computed: waking cortisol level, area-under-the-curve (AUCg) each day, and diurnal slope (first to last sample, including individual regression slope). Participants also reported health behaviors (sleep quality, exercise, alcohol use) and treatment history. Pearson correlation analyses assessed associations between cortisol metrics and psychosocial, demographic, and clinical variables (p 0.05). Results Participants had a mean age of ∼56 years and were ∼11 months post-treatment; 42.7% had Stage II disease. Average cortisol output was moderate (mean AUCg 7 with large variability) and diurnal slopes were negative (–0.17) on both days, indicating the expected decline from morning to evening. Several associations were observed between cortisol patterns and patient factors. History of chemotherapy or radiotherapy was associated with a less steep Day 1 cortisol decline (flatter slope). Better sleep quality correlated with higher Day 1 cortisol AUCg, more exercise was linked to a steeper Day 2 decline, and higher alcohol use was associated with a flatter Day 2 slope. Conclusions This study is the first to characterize diurnal cortisol profiles in CABCS, providing novel insights into HPA axis regulation in an underserved survivor group. The associations of cortisol rhythms with treatment exposures and lifestyle factors suggest that both cancer-related and behavioral influences shape cortisol regulation in this population, with implications for understanding biologic stress in the context of cancer health disparities. Targeted strategies to reduce stress and modify health behaviors may improve HPA axis function and survivorship outcomes in minority breast cancer survivors. Citation Format: Eunju Choi, Celia Wong-Meli, Qian Lu. Diurnal cortisol profiles of Chinese American breast cancer survivors abstract. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr C037.