A strong positive correlation between the MDSC percentage and neutrophil/lymphocyte rate (NLR) (a prognostic marker in both ipilimumab and nivolumab therapy) has also been investigated in patients with breast cancer and non-small cell lung carcinoma [78,79] following PD-1 therapy, showing a correlation of the clinical response with decreased MDSCs or a decreased neutrophil/lymphocyte ratio. Here, PDCD1 is linked to breast carcinoma.