Welcome Edward, and congratulations on completing treatment!

I know you meant EBRT, an acronym for External Beam Radiation Treatment, such as IMRT that most everyone has, which is radiation delivered outside the body. Radiation continues to work in the body for weeks after treatment, and was once told by my RO, Radiation Oncologist, it continues to work for six weeks, just about as long as you had treatment, and another RO said for 2 weeks they know, and past that it's theoretical.

PET scans are usually done minimum 11 weeks after radiation treatment completion to avoid false positives like seen on the CT scan, but they can have them too due to it being highly sensitive showing any "uptake" from inflammation, fibrosis, infection, called SUV, Standardized Uptake Value, so proper patient preparation, it's delivery, and an experienced radiologist reading them are important.

As mentioned, no scanning can prove cancer 100%, only a biopsy can, and that is subject to error too. Even FNAB can show mixed morphology after treatment, indicating cancer, but further analys shows it's not.

I suggest everyone get a copy of any scan report from their doctor, and a CD copy of the scan right after its done at the radiology center, which takes 10 minutes, for your records, and future reference. I take them to all my doctor visits right after any testing, but only my ENT or Radiation oncologist look at the disc, which require specialized training. Other doctors look at the interpretation report, and copy it for their files, if their not in the same hospital system, and most were glad I brought them.

Radiation has acute toxicities, which gradually subsides after several months, and then there are long term toxicities sometimes lasting for months, even years, and can take up to two years to fully recover, but it's hard to give any timing as everyone is different with the location of their cancer, type of radiation, the dosage amount, Frequency, where radiated, Bilaterally. if with chemo or not, and other cormorbidities.

All the things you mention, edema, anxiety, dry mouth, weight loss, and depression are common, and can be treated or impact lessened. We can go over any you have difficulty with further, and Christine has suggested a few things. I think I'm a champ with weight loss lol, lost over 110lbs just from chemo, and gained 50lbs back. Christine has a high calorie protein shake that can help too.

One of the biggest prognostic factors is being HPV positive or not. At this time, I believe testing is required or suggested for all oropharyngeal cancers, such as base of tongue, and tonsil cancer. You can inquire about this with your doctor, and if not, they can still test the biopsy sample.

Waiting is the worst! Try to occupy your time with any hobbies, light exercise such as walking does wonders, even posting here to vent or ask any question.

All the best!