Clear pet scan with metastatic cancer, what does it mean?

Uptake not useful: Pet scan usually use a radioactive sugar to go where tumors are based on the idea that a very active cancer is using up a lot of energy to grow, so suger is going to the same place. Some tumors just don't concentrate the agents in pet scans much over background. It can mean the tumor is slow growing. But it doesn't have to mean that. Small lesions can often just not be big enough.

PET scan: Pet scans are often used to look for metastatic disease and a clear scan means no obvious disease noted, a good sign but does not always guarantee one is disease free.