Often when doctors determine if a patient may respond to standard immune checkpoint therapy, mainly meaning PD-1 inhibitors, Opdivo or Keytruda, they look at the PD-L1 status of the tumor. This is to see if the tumor has the receptor PD-L1, which correlates with blocking the corresponding receptor PD-1, removing one of the potential “brakes” of the immune system. We know, however that this is an imperfect marker; patients can respond with our without PD-L1 expression on the tumor, though generally, ones that do express PD-L1 would have a higher chance to respond. One study had even indicated that PD-L1 expression on the macrophage was more predictive than the tumor, but this is not what is used. In addition, looking at DNA repair genes, known as MMR, is another, though very rarely do patients have this. The other is tumor mutational burden. However,, we also know other gene mutations are associated with improved responses, but they are not used as selection criteria to give patients immunotherapy. This means that some patients who may respond are missing out. One of these described in a study published by Sarfatay, et al discusses a mutation in the gene ARID1A in cases of bladder cancer. We know it is probably any cancer, not just bladder. Patients with an ARID1A mutation may have a better chance to respond, and certainly should be considered for immunotherapy. Unfortunaltey, this still does not fit in the selection criteria for insurance coverage.