SU-E-J-199: A Novel Method to Evaluate Local Control and Recurrence Using 18F-FDG PET After Lung SBRT

The goal of this study is to evaluate the predictability of a novel method using a self background-corrected maximum Standard Uptake Value (cSUVmax) from 18F-FDG Positron Emission Tomography (PET) of the patients following lung cancer stereotactic body radiosurgery (SBRT).

20 qualified patients treated out of 38 patients treated with SBRT for a single lung malignant lesion between May 2009 and December 2009 were enrolled in the cohort study. All had pre- and at least one post-treatment PET images available at the time of study. The mean normal tissue SUV from the descending aorta was sampled as baseline to divide SUVmax of tumor site. The resultant cSUVmax was used for assess the local control or possible recurrence. The Result was then compared with that using SUVmax alone method.

The average follow-up length was 48.9 weeks ranging from 18.6 to 115.0 weeks. The mean SUV of aorta was measured as 1.821±0.364, ranging from 1.173 to 2.576. From the pre-treatment PET, 70% and 65% was indicated positive correspondingly when using SUVmax with 2.50 and cSUVmax with 1.52 thresholds. When PET was taken < 29 weeks post-SBRT, 75% and 67% respectively showed higher values in the locally controlled group. For PET = 29 weeks after SBRT, with cSUVmax both locally controlled and recurrent groups are accurately identified, while SUVmax shows 5% false positive and one possible false negative.

The SUVmax in lung tumor site corrected by the mean SUV of descending aorta or cSUVmax provided a more reliable parameter than using SUVmax alone in predicting the local control and recurrence for follow-up PET of patients after lung SBRT. The method used in this study objectively displayed a strong correlation between low cSUVmax and local control following lung SBRT in this investigation, otherwise a local recurrence is suggested.