Examples are variants in ABCB1 that can predict toxicity and response to chemotherapy in breast cancer (Xiao et al. 2020) and ABCG2 and ABCC10 variability that associates with tyrosine kinase inhibitor and taxane toxicity in non-small cell lung cancer (Noguchi et al. 2014; Sone et al. 2019). The gene discussed is ABCG2; the disease is breast carcinoma.