PT  - JOURNAL ARTICLE
AU  - Sonya Park
AU  - NEGIN HATAMI
AU  - Omar Rutledge
AU  - Norman Koglin
AU  - Billy Loo
AU  - Alice Fan
AU  - Erik Mittra
TI  - Pilot study of <sup>18</sup>F-FSPG vs<sup>18</sup>F-FDG PET imaging for response assessment in cancer
DP  - 2017 May 01
TA  - Journal of Nuclear Medicine
PG  - 118--118
VI  - 58
IP  - supplement 1
4099  - http://jnm.snmjournals.org/content/58/supplement_1/118.short
4100  - http://jnm.snmjournals.org/content/58/supplement_1/118.full
SO  - J Nucl Med2017 May 01; 58
AB  - 118Objectives: 18F-FDG PET/CT is widely used for therapeutic response assessment in many cancers, although the change can vary greatly depending on the type of treatment (chemotherapy vs. immunotherapy or radiotherapy). 18F-labeled FSPG, an L-glutamate derivative, has shown to be a promising radiotracer for PET imaging of the amino acid antiporter system xC- that is involved in detoxification processes and balancing oxidative stress. This prospective pilot study is the first to evaluate the utility of 18F-FSPG PET for response assessment following therapy, in comparison to 18F-FDG.Methods: Seven patients were enrolled in this study, including three renal cell cancer (RCC) patients treated with an investigational glutaminase inhibitor and four non-small cell lung cancer (NSCLC) patients treated with external beam radiation therapy. 18F-FDG and 18F-FSPG scans were taken within 1 month of each other, once at baseline and again after treatment. Maximum standardized uptake value (SUV) and bidimensional size were measured for up to six of the hottest lesions on each scan.Results: A variety of treatment responses were seen. Two patients with favorable response to therapy showed similar response on 18F-FDG and 18F-FSPG scans. Of two patients who had worsening disease, one showed discordant findings with decreasing 18F-FDG but increasing 18F-FSPG uptake, while the other showed progression on both 18F-FDG and 18F-FSPG, although more new lesions were identified on the latter. Another patient had stable disease, which was demonstrated as such on 18F-FDG, but had no uptake with 18F-FSPG. Two patients have not yet had their post-treatment FSPG scans. Notably, one has multiple known hepatic metastases that were not 18F-FDG-avid or 18F-FSPG-avid.Conclusion: This pilot study shows some similarities as well as discordance in response assessment between 18F-FDG and 18F-FSPG likely relative to their alternative mechanisms of uptake. Additional studies are needed to better understand these differences and their clinical utility. Research Support: