Feliciano EMC, Chen WY, Lee V, et al. - In this cohort study involving 1,395 patients [mean (SD) age at diagnosis was 52.8 (10.2) years] with nonmetastatic breast cancer, researchers ascertained if body composition was correlated with relative dose intensity (RDI) on anthracycline and taxane-based chemotherapy or hematologic toxic effects and if lower RDI mediates the relationship of adiposity with mortality. Between February 25 and September 4, 2019, data analysis was performed. Lower RDI has been associated with excess adiposity, presenting as larger visceral or intramuscular adiposity. The correlation of adiposity with worse breast cancer–specific survival was partly mediated by lower RDI. Body composition may help to identify patients who are likely to experience toxic effects and subsequent dose delays or reductions, which could jeopardize the effectiveness of chemotherapeutics.