Ethnic disparity in chemotherapy–induced febrile neutropenia incidence in Asian breast cancer patients: A retrospective cohort study

Background: Majority of published findings on chemotherapy–induced febrile neutropenia (FN) are restricted to three ethnic groups: Asians, Caucasians, and African Americans. In this two–part study, we examined FN incidence and risk factors in Chinese, Malay and Indian chemotherapy–treated breast cancer (BC) patients in Southeast Asia. Methods Hospital records or ICD codes (fever:ICD9/10:2880/D70 and neutropenia:ICD9/10:7806/R509) were used to identify patients with FN, during or within 30 days from the last chemotherapy session. In both Singapore Breast Cancer Cohort (SGBCC) and Joint Breast Cancer Registry (JBCR), time to first FN from start of chemotherapy was estimated using Cox regression. Multinomial regression was used to evaluate differences in patient, tumour, and treatment characteristics across ethnicities. Results FN was observed in 170 of 1,014 patients (16.7%) in SGBCC. Cox model showed that non–Chinese were at higher risk of developing FN (HR Malay [95% CI]:2.04[1.44–2.88], p < 0.001; HR Indian 1.88[1.11–3.18], p = 0.018). In JBCR, FN was observed in 965 of 7449 patients (13.0%). Indian patients, lower baseline absolute neutrophil count, non– luminal A proxy subtypes, and anthracycline–containing regimens were identified as risk factors for FN in the univariable Cox models. Disparities across ethnicities risk (HR Malay 1.29 [1.07–1.54], p = 0.006; HR Indian 1.50 [1.19–1.88], p < 0.001) remained significant even after further adjustments. Finally, age–adjusted multinomial model showed that as compared to Chinese patients, non–Chinese (OR Malay vs Chinese(ref) 3.65[1.45–9.16],p = 0.006;OR Indian vs Chinese(ref) 4.43[1.45–13.60],p = 0.009) were significantly more likely to develop multiple episodes of FN during treatment. Conclusion Ethnic differences in chemotherapy–induced FN among BC patients exist. Further studies can focus on investigating pharmacogenetic differences across ethnicities.