Serial Evaluation of Increased Chest Wall F-18 Fluorodeoxyglucose (FDG) Uptake Following Radiation Therapy in Patients With Bronchogenic Carcinoma

PURPOSE: Following radiation therapy for bronchogenic carcinoma, increased FDG accumulation within the irradiated tissue can be identified. This finding has not been well characterized. Therefore, we retrospectively evaluated the time course, frequency, and intensity of increased FDG uptake over a one-year period in patients who had been treated with radiation therapy. MATERIALS AND METHODS: Serial FDG-PET studies (n = 38) were performed in patients (n = 12) with bronchogenic carcinoma before and after radiation therapy. Regions of interest (ROIs) were placed in the chest wall and activity concentrations of posttherapy studies were compared to pretherapy studies. FDG uptake was also described qualitatively relative to mediastinal activity (1-4 scale) by two observers blinded from clinical information. RESULTS: Chest wall radiation port ROI uptake was 18% higher in the 2-month (P = 0.08), 40% higher in the 6-month (P = 0.003), and 32% higher in the 12-month (P = 0.04) posttherapy studies than in non-port ROIs. In 6 patients that clinically had radiation-induced chest wall fibrosis or pneumonitis, visual interpretation identified abnormal chest wall or pleural region FDG uptake in 5/6. In 2/6 patients without clinical chest wall fibrosis, abnormal, chest wall FDG uptake was seen. CONCLUSIONS: Radiation therapy occasionally causes modestly increased soft tissue FDG uptake within irradiated soft tissue in patients being treated for bronchogenic carcinoma, which persists for up to one year after therapy.