Rolanda,
Here is a link of the National Comprehensive Cancer Network members:
http://www.nccn.org/members/network.asp It sounds like the doctors are not sure of what they want to do or lack experience in treating this kind of cancer. I am not judging them and I know something could have been filtered in the translation through you. A second opinion could give you the peace of mind you need right now.
I know methadone is used a lot for patients in hospice as well as initially used to keep heroin addicts off of heroin. I have not, however, heard too many oral cancer patients being put on methadone. There are more cases of using the Fentynal (Duragesic) patch as it is time release and helps the patient stay a bit more lucid than more intense narcotics.
I know all of us, patients, caregivers, family and friends, have the fear of the big shoe dropping from the point of cancer diagnosis forward. A doctor mentioning the "calm before the storm" from PET scan results with a negative biopsy would scare me to death, too.
From your post, I would seek out someone with much more experience with this type of cancer before I let my mind wander too much. For instance, I had the cancer spread to two lymph nodes before I was diagnosed and the battle had not even started. Even my post treatment PET scans have had areas of concern but with very experienced eyes reviewing them, the areas have not grown and all eyes believe there is no recurring cancer.
I am sorry you had such a scare so soon after treatment while the nerves are still somewhat raw. Get an opinion from an experienced medical team and you will be in a better position to determine what might be the proper course of action.
Welcome to the neighborhood!
Ed