Can Memory Loss Be Treated By Avastin After Radiation For Tumor?

my huband was diagnosed with gbm may 22, 2010. he had his tumor removed underwent radiation, chemo w/temodar & avastin. He has now completed his first round of maintenance avastin which he only takes once a month. the pet scan on aug 6,2011 didnt show any signs of cancer. the mri on oct 10 showed a small white ring which dr thinks is scar tissue, he is treated at duke. ive noticed hes had problems with short term memory. will his memory get better with avastin? and do you think it is scar tissue? dr said she didnt think it could be cancer cells waking up because the pet scan was clear in aug. i am the mother of 2 boys, my husband is 46. i just feel like i need to be prepared for everything. my husband is in denial, he thinks if we dont acknowledge it then its not there but i have to know what to expect. could this be the beginning of tumor reoccurance? thanks for your help! Cheryl