Predictive role of 18F-FDG-PET/CT 1 month before and after hypofractionated stereotactic body radiation therapy for stage I non-small cell lung cancer

Abstract

7569 Background: To know the predictive role of 18F-FDG-PET/CT 1month before and after stereotactic body radiation therapy (SBRT) to stage I non-small cell lung cancer (NSCLC). Methods: Between 2004 and 2007, 20 patients received SBRT with 48 Gy for 4 consecutive days and checked two times of FDG- PET/CT and chest CT with contrast-enhancement at 1 month before and after SBRT. Change of maximal SUV (SUVmax) on FDG-PET/CT and the longest tumor diameter on chest CT before and after SBRT was measured. Patients only with high FDG uptake, SUVmax 3.0 or above, on FDG-PET/CT before SBRT and tumor diameter below 5 cm were analyzed in this study. Change of tumor diameter was classified to PR (partial response), SD (stable disease), and DP (disease progression) as RECIST criteria and change of SUVmax was described as % change. Chest CT was checked at every 3 or 6 months during follow-up. Results: Mean time intervals from SBRT to FDG-PET/CT and chest CT were 32 and 30 days respectively. Mean longest tumor diameter was changed from 2.59 cm (1.36–3.93) to 2.17 cm (1.18–3.41), and its reduction rate was -16.2%. By RECIST criteria, 4 patients showed PR, 15 patients showed SD, and other 1 patient showed DP. Mean decrease rate of SUVmax on FDG-PET/CT was -52.1% and its mean value was changed from 7.1 (3.2–13.1) to 3.4 (0.3–9.8). Median follow-up time was 16 months. Local tumor progression developed in 2 (10%) patients and time to progression was 3.4, 6.1 months. Tumor responses on post-SBRT chest CT were PR in 1 and SD in the other 1 patient, and SUVmax changes were -31.9%, -25.5% in each. Most of patients showing no response, SD or DP, didn't recur after SBRT, and so chest CT at 1 month could not predict actuarial tumor response. On the contrary to chest CT, no patients showing SUVmax decreases over 40% experienced tumor progression after SBRT. High decrease rate of SUVmax over 40% decrease on FDG-PET/CT 1 month after SBRT could warrant good actuarial local tumor control earlier. Conclusions: Change of SUVmax on FDG-PET/CT 1 month before and after SBRT could predict actuarial local tumor control of stage I NSCLC earlier and 1 month after SBRT was adequate timing for the earlier evaluation of tumor response. No significant financial relationships to disclose.