At last report with MEDX/BMY ipi, I seem to remember reports of complete response lasting for at least a year---all signs of tumor disappeared with that immune therapy mab[was it combined with something else besides the steroid to control AEs? I do not recall after 3 years last reading]. Earlier the initiation of treatment, the better the result. Better diagnostic imaging might give more definitive info today.
I suggest you read Thorpe's paper using radiation in the rat model of glioblastoma. The radiation increases the amount of PS on the tumor vasculature and tumor cells, as does the chemotherapy. That is why bavi has to be used with one or the other, to increase the amount of target PS. In that paper, and Thorpe also showed a slide of the survival in the NYAS webcast, it is shown that 13% of the rats became immune to the glioblastoma.