Is it progression, necrosis or could it really be Opdivo working on brain mets? - 1293557

In October 2013 our 23 year old son with was diagnosed with stage 4 poorly differentiated Neuroendocrine Lung Carcinoma with mets everywhere - lung primary, liver, adrenals, kidneys, pancreas, bones and various other places - too many tumors to count. He had treatments of temodar, carboplatin & etoposide, affintor and WBRT for multiple brain mets. None of these treatments produced any reduction with small exception of WBRT. He dropped significant weight. Our Oncologist had no further options. Wonderful man that he is he did offer to go to BMS and apply for compassionate care as we go to a large cancer center in Virginia and they run numerous trials there. Little did we know our son would become a Super Responder. Now almost all of his tumors & mets are gone beginning at the 3rd to 4th infusion. He just finished his 59 infusion and has never had any side effects from the immunotherapy. He does have one Major issue - that being the brain mets. In January 2017 he had SRS to both his brain for mets and one spinal met. The spine is fine but in August he started experiencing numbness, weakness in limb and a droopy smile on left side. MRI revealed that the brain met of 7mm that was SRS was back, 2cm, very inflamed and causing his issues. Had brain surgery and we found out it was necrosis. they went back in the next morning and removed necrosis and did tell us no way to be able to remove all cells which we knew. In November a follow up MRI revealed worse inflammation, edema in the same cavity where necrosis was and 2 other mets showed up 6 and 7 mm also inflamed with edema and 5 other small mm ones. The irony is he has no symptoms at all and feels fantastic. ? Is it possible with the back to back brain surgeries within 27 hours that opdivo finally was able to successfully cross the BBB? We rescan next month and we are told it is necrosis, progression or the Nivolumab could have made it in substantial amount and is attacking every tumor it sees. Your opinion?