Mismatch repair deficiency however remains only one predictor of response to checkpoint inhibition, with studies in urothelial cancer suggesting that harbouring a CDKN2A mutation reduces benefit from checkpoint inhibition, although this may be tumour specific as a second study in melanoma found no link between either CDKN2A or TP53 and clinical outcome following immunotherapy.88,89. The gene discussed is TP53; the disease is neoplasm.