If you go to the place of testing, they can give you a copy of the PET report, if you care to know sooner. Hard to say what they are concerned about, but light evidence may be slight uptake in the PET, increase or no shrinkage at tumor sight? Anyway, no scan can prove cancer 100 percent, and after surgery, chemoradiation, it is difficult to differentiate scar tissue from a malignancy, and may show false positives, that's why they want to do another CT to see if there is any change from now, and the next scan, but dates seem a little far to see the dr. Maybe they can do an MRI now, but each are good in certain aspects. Best of luck.