PDCD1 and breast carcinoma: Kraya et al [40] reported that in BRCA1/2 breast cancers that HRD scores and hormone receptor subtype were predictive of immunogenicity resulting from their increased genomic instability making them theoretically more sensitive to checkpoint inhibitors, although in practice only 20% of patients with BRCA1/2 mutations respond to PD-1/PD-L1 inhibition suggesting that a combination of factors involving BRCA1/2 status, HRD and hormone receptor status may more effectively predict breast cancer patients who will respond to checkpoint inhibitors than any one factor alone.