893 poster NON-GATED F-18 FDG PET/CT FOR TARGET VOLUME DELINEATION IN STEREOTACTIC BODY RADIATION THERAPY (SBRT) IN PATIENTS WITH STAGE I NON-SMALL CELL LUNG CANCER (NSCLC) OR HYPERMETABOLIC OLIGOMETASTATIC LUNG LESIONS

Corresponding Author: Michael Schmuecking, MD E-Mail: michael.schmuecking@insel.ch Inclusion criteria: Informed consent, histologically proven NSCLC stage I or hypermetabolic oligometastatic lung lesions. Peripheral or central localization, maximal tumor diameter of 45mm. Karnofsky index > 60%. Medically inoperable. Moving of the lung lesion during breathing less than 5mm as detected by 4D-CT. Initial staging: whole body 18F-FDG PET/CT in radiation treatment position, MRI of the brain. Optional for staging: 18F-FDG PET/CT of the lung in breath hold technique in radiation treatment position. Radiation treatment planning: 4D-CT and angio-CT in radiation treatment position for target volume delineation. BodyFIX® vacuum cushions for comfortable, accurate and reproducible patient positioning during radiation treatment. Using 4DCT for target volume delineation, a Boolean operation was used to sum the multiple gross target volumes (GTV) delineated in diagnostic lung window to form an internal target volume (ITV). The planning target volume was derived by a three-dimensional isotropic expansion of the ITV by 5mm to account for both microscopic extension and daily setup errors. Using non-gated PET/CT (frame mode) for target volume delineation of the ITV the iso-line of SUV 2.5 was used or the tumor/background algorithm as proposed by Nestle et al. JNM 2005. For 16/22 lung lesions the prescription dose was 5 x 12 Gy, for 1/22 centrally located lung lesion the prescription dose was 5 x 10 Gy, for the initial 5/22 lesions the prescription dose was 5 x 7 Gy. For all patients the prescription isodose was the 80% line (prescription line identical with the planning target volume). Maximal time for follow-up: 21 months, mean time for follow-up: 13 months. By design, stereotactic body radiotherapy (SBRT) is applied to small treatment volumes, using fewer but significantly higher dose fractions, and steep dose gradients – all of which act to maximize cell kill and minimize the risk of damage to the surrounding normal tissues.