What is a characteristic finding in post-chemotherapy PET scans?

In the context of post-chemotherapy PET scans, a decrease in FDG uptake is the expected finding. This reduction occurs because chemotherapy often successfully kills cancer cells, resulting in lower metabolic activity in the affected areas. Since FDG (fluorodeoxyglucose) is a radiotracer used to visualize glucose metabolism, areas with lower metabolic rates will show decreased uptake.

This pattern is particularly important in the assessment of treatment response. A significant decrease in FDG uptake on PET scans can indicate a positive response to chemotherapy. Furthermore, after treatment, inflammation or necrosis (tissue death) can also affect FDG uptake, but generally, the trend will favor decreased uptake as cancer cells are eliminated.

In contrast, increased FDG uptake would typically suggest ongoing metabolic activity, which could indicate residual disease or recurrence. Normal FDG uptake does not provide useful information regarding tumor activity post-treatment, and localized FDG uptake can suggest specific areas of concern but is not a definitive characteristic finding after chemotherapy. Thus, decreased FDG uptake is the most characteristic finding in post-chemotherapy evaluations.