I believe that it's balancing the risk of the additional PET/CT radiation vs. the benefit of using it to check up on the more advanced (by T or N) cancer.

When my husband was initally checked out for a mystery earache, the CT scan showed a swollen node, but no tumor. His doctor at the HMO we belong too did a FNA of his swollen node - fluid came out, but it was clear for cancer and infection. The needle didn't hit the cancerous part. He also tried to do an in office throat biopsy - couldn't because of his gag reflex. If he had, that would have been negative too, because the cancer was not at the surface. Thank heavens, he didn't like the look of it, and escalated to the team at MetroHealth - otherwise he could have had 2 biopsies that showed nothing and stage III or IV cancer (depending on if a second node was involved or just signaling). Thats a long story, but what it boils down to is that I've got a lot of respect for a doctor's hands, mind and intuition - as well as for advanced diagnostic technology.

Forgot about the doctor's eyes and ear - a good one will look at the whole patient, and listen carefully to him or her. If the patient doesn't look too perky, or sounds unusually negative, there may be a clue that something is amiss. I like the thought of clear scans, but I am also happy when the doctor is satisfied at the end of the exam.