Tumor inflammation and pseudo-progression, which are often seen on imaging, may cause additional symptoms and make tumor growth assessment difficult.61 The ability to successfully target brain metastases only among certain patients, such as those expressing high levels of PD-L1, may be a potential limitation of checkpoint inhibitors.62 These limitations are significant in some patients to the degree that they may have little to no benefit from the currently available checkpoint inhibition therapies. This evidence concerns the gene CD274 and neoplasm.