In the discovery cohort, 18 genetic variations in genes encoding four NRs (HNF4α, PXR, PPARs, and VDR), one transcription factor (NF-κB), and one cytokine (TNF) emerged as significant (p < 0.05) predictors of severe neutropenia over the entire course of chemotherapy. This evidence concerns the gene NR1I2 and Decreased total neutrophil count.