My understanding is that the most definitive way of diagnosing cancer is with a biopsy. Having said that, CT and PET can help the doctor to know where to take the biopsies. If he recommends more biopsies after the PET I would get them done. They are fairly easy and cheap unless he has to put you out for them.

In 1994 I found a 3cm tumor on my right tonsil. After 3 rounds of chemo, I underwent a radical neck dissection with a peck flap. I had a reoccurance which required twice a day radiation treatments and then had 19 years cancer free. I then found a very small tumor on my right tonsil. It was removed. Then I found a 1 cm mass near the base of my tongue on the left side. I had two partial glossectomys with bad margins and then then underwent Brachytherapy.