GC and neoplasm: In the current study, the nivolumab plasma levels in a real-life context of NSCLC are described at different timings and, in addition, the role of 25-VD concentrations and VDBP rs7041 A > C SNP in predicting concentrations lower than 18.7 μg/mL (the cut-off value associated with tumor progression as shown by Stijn et al. [6]) is suggested.