Dok, I think I can offer some info on necrosis. My nephew had Medulloblastoma, similar but not as bad as Glioblastoma. They did surgery to remove the largest tumor from his brain stem. After that, he had successful radiation and chemo treatments. On one of his follow up MRI's, the found a couple of little things. Turned out to be necrosis thankfully. The dead pieces of small tumors in his spine were of no concern to the doctors once they were sure the cancer was not active. So, I would assume any necrosis would not be a worry unless it is so large as to cause other symptoms/impairments. Hope that helps.