Elens et al. (2013b) used the CYP3A golden standard phenotyping probes midazolam and erythromycin as indicators for the in vivo effect of CYP3A4∗22 on drug metabolism, showing that cancer patients carrying CYP3A4∗22 had a 40% reduction in erythromycin clearance and a 21% lower midazolam metabolic ratio (MR) (Elens et al., 2013b) (Supplementary Table 1). This evidence concerns the gene CYP3A4 and cancer.