@article {Lizarraga30, author = {Karlo J. Lizarraga and Martin Allen-Auerbach and Johannes Czernin and Antonio A.F. DeSalles and William H. Yong and Michael E. Phelps and Wei Chen}, title = {18F-FDOPA PET for Differentiating Recurrent or Progressive Brain Metastatic Tumors from Late or Delayed Radiation Injury After Radiation Treatment}, volume = {55}, number = {1}, pages = {30--36}, year = {2014}, doi = {10.2967/jnumed.113.121418}, publisher = {Society of Nuclear Medicine}, abstract = {Brain metastases are frequently treated with radiation. It is critical to distinguish recurrent or progressive brain metastases (RPBM) from late or delayed radiation injury (LDRI). The purpose of this study was to examine the diagnostic accuracy as well as the prognostic power of 6-18F-fluoro-l-dopa (18F-FDOPA) PET for differentiating RPBM from LDRI. Methods: Thirty-two patients who had 83 previously irradiated brain metastases and who underwent 18F-FDOPA PET because of an MR imaging{\textendash}based suggestion of RPBM were studied retrospectively. PET studies were analyzed semiquantitatively (lesion-to-striatum and lesion-to-normal brain tissue ratios based on both maximum and mean standardized uptake values) and visually (4-point scale). The diagnostic accuracy of PET was verified by histopathologic analysis (n = 9) or clinical follow-up (n = 74) on a lesion-by-lesion basis. Receiver operating characteristic curve analysis was used to identify the best diagnostic indices. The power of 18F-FDOPA PET to predict disease progression was evaluated with the Kaplan{\textendash}Meier and Cox regression methods. Results: The best overall accuracy was achieved by visual scoring, with which a score of 2 or more (lesion uptake greater than or equal to striatum uptake) resulted in a sensitivity of 81.3\% and a specificity of 84.3\%. Semiquantitative 18F-FDOPA PET uptake indices based on lesion-to-normal brain tissue ratios were significantly higher for RPBM than for LDRI. Among the various predictors tested, 18F-FDOPA PET was the strongest predictor of tumor progression (hazard ratio, 6.26; P \< 0.001), and the lesion-to-normal brain tissue ratio or visual score was the best discriminator. The mean time to progression was 4.6 times longer for lesions with negative 18F-FDOPA PET results than for lesions with positive 18F-FDOPA PET results (76.5 vs. 16.7 mo; P \< 0.001). 18F-FDOPA PET findings tended to predict overall survival. Conclusion: Metabolic imaging with 18F-FDOPA PET was useful for differentiating RPBM from LDRI. Semiquantitative indices, particularly lesion-to-normal uptake ratios, could be used. A visual score comparing tumor 18F-FDOPA uptake and striatum 18F-FDOPA uptake provided the highest sensitivity and specificity and was predictive of disease progression.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/55/1/30}, eprint = {https://jnm.snmjournals.org/content/55/1/30.full.pdf}, journal = {Journal of Nuclear Medicine} }