Finally, because the study population was limited to patients with selected metastatic cancers who received chemotherapy at four US health systems, our study population may not reflect the population of patients treated in clinical practice across the USA; additional research using data from other large populations is needed to validate the applicability and accuracy of the characterization of G-CSF use, FN incidence, and FN-related outcomes reported in this study. The gene discussed is CSF3; the disease is metastatic malignant neoplasm.