Distinguishing Post-treatment Changes from Malignancy at FDG PET/CT

The differentiation of post-treatment changes from residual/recurrent tumor presents a major problem in the treatment of patients with cancer. Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) is used to differentiate between them. A main indication of FDG PET/CT is restaging disease after primary treatment, which could comprise of surgery, chemotherapy or radiation therapy, or various combinations of these. It is imperative for the PET reviewer to consider the clinical scenario and treatment history when interpreting PET findings. A wide range of oncologic treatment– related effects, such as surgery or radiation- induced  inflammation,  drug  toxicity, pseudoprogression, and hematopoietic rebound, can manifest as regions of increasing FDG activity and may be mistaken for new or progressive malignant foci. Appropriate and timely imaging following initial treatment is important to detect residual or recurrent
disease to initiate additional therapy, which can prolong disease free survival and improve quality of life.
The aim of this lecture is to review some of common oncologic treatment- related changes at FDG PET/CT, and the utility of FDG- PET/CT in these patients to detect malignant disease