Body composition, chemotherapy dosing and hematologic toxicity among Black and non-Black women being treated for breast cancer.

INTRODUCTION: Black women in the United States have higher breast cancer mortality rates compared to women of other races/ethnicities. Heterogeneity in body composition between Black and non-Black women may contribute to differences in relative drug dosing and chemotherapy toxicities, leading to treatment delays and lower treatment completion rates. This study evaluated the extent to which drug dose/kilogram (kg) fat free mass (FFM) differs by race, and whether measures of FFM or adipose tissue (AT) are independently and/or jointly associated with hematologic toxicity, treatment delays, treatment discontinuation, and relative dose intensity (RDI). METHODS: Women who were treated with neo/adjuvant anthracycline- and/or taxane-containing regimens for breast cancer between 2012-2019 and had an abdominal CT scan within 12 weeks of chemotherapy initiation were included in this retrospective study. Visceral and subcutaneous AT area and FFM were measured using CT scan slices at the L3 vertebra level. RESULTS: A total of 230 women met the inclusion criteria. On average, Black women were older and had higher weight, FFM and AT compared to non-Black women; however, Black women had lower percent FFM. No statistically significant differences in initial or cumulative drug dose/kg FFM were observed between Black vs non-Black women for any individual drug. Similarly, neither FFM or AT were independently or jointly associated with incidence of hematologic toxicity, treatment delays or discontinuation for any individual chemotherapy drug. CONCLUSION: Current BSA-based chemotherapy dosing regimens do not appear to contribute to disparities in treatment-associated toxicity or chemotherapy completion.