By 8 weeks some say the PET/CT is 90% accurate, after treatment, Four months is even better, and by a year it's 100% accurate. Anything over an SUV of 2.0 is suspicious for cancer, but other factors are considered, such as surgery, inflammation, infection, treatment etc, and as Uptown said, needs further attention, and like your doctors are doing. I had uptake in the lymph node on my right side, 1.3, and tongue 3.1, most likely due to an incisional biopsy done on the tongue a month earlier, and had a negative nodal FNAB. In the same scan a left node was with an SUV of 1.6 that was postitive for cancer with an FNAB on follow-p. A PET/CT scan can detect cancer as small as 5mm. A CT scan can go as low as 1cm. I had an MRI that didn't pick up cancer, but a PET/CT did.

Good luck.