Necrosis or Tumor Progression? - 1254548

My 27 year old son is 35 months since having an AA3 tumor removed (left frontal lobe) followed by standard care Temodar and radation. December's MRI showed 2 small areas of enhancement for the first time. In the follow up MRI in late February they increased in size from 2 and 3 mm to 6 and 7 mm, and as a result he was put back on Temodar for 6 months (5 on, 23 off). While they don't know if this is necrosis or a recurrance, I'm assuming they are being aggressive and treating it as if it is a reoccurance. My fear is that it is a recurrance but I'm wondering how likely is it that this is necrosis? In a 9 week period if the enhancing areas increase from 2 and 3 mm to 6 and 7 mm after 33 months of nothing happening, can necrosis behave this way, or is it more likely 2 tumors growing in the area where he had 1 removed that was 5 1/2 cm. Will the temodar be as effective now as it seemed to be a few years ago? Thanks you very much!