PDCD1 and metastatic melanoma: Of note, the two subjects who received both pembrolizumab and nivolumab (in addition to GKRS) were placed into the less-than-six-weeks category, as pembrolizumab was administered within one month from completion of GKRS for both patients. According to Alormari, et al., early signs of radiation-induced changes were noted in a subject with cerebral metastatic melanoma who received GKRS and PD-1 immunotherapy separated by less than four weeks [5].