PET scans are somewhat controversial on this forum. Used within a few months after radiation they are prone to false positives and need to be read by someone who has LOTS of experience with head/neck cancer. Radiologists like that do not work in the community hospital. Most will 'cover' themselves with summaries like "inconclusive". Take that scan to another more experienced radiologist in a cancer center.

I too had post treatment biopsies (tongue) instead of scans. Tissue samples are the ONLY way to conclusively diagnose the presence or absence of cancer.

Get multiple opinions on every step of the process. Its never too late to get another opinion. Travel if you need to, but get those additional perspectives. It is time and money very well spent. Be strong. Tom