Uptake of ¹⁸F-fluorocholine, ¹⁸F-FET, and ¹⁸F-FDG in C6 gliomas and correlation with ¹³¹I-SIP(L19), a marker of angiogenesis

Targeting extracellular structures that are involved in angiogenic processes, such as the extra domain B of fibronectin, is a promising approach for the diagnosis of solid tumors. The aim of this study was to determine uptake of the ¹⁸F-labeled PET tracers ¹⁸F-fluorocholine (N,N-dimethyl-N-¹⁸F-fluoromethyl-2-hydroxyethylammonium), ¹⁸F-fluoro-ethyl-L-tyrosine (FET), and ¹⁸F-FDG in C6 gliomas of the rat and to correlate it with uptake of the anti-extra domain B antibody ¹³¹I-SIP(L19) as a marker of neoangiogenesis. Methods: C6 gliomas were orthotopically induced in 17 rats. Uptake of all tracers was measured using quantitative autoradiography, and uptake of ¹⁸F- fluorocholine, ¹⁸F-FET, and ¹⁸F-FDG was correlated with uptake of ¹³¹ISIP( L19) on a pixelwise basis. Results: The mean ¹³¹I-SIP(L19), ¹⁸F-fluorocholine, ¹⁸F-FET, and ¹⁸F-FDG standardized uptake values in the tumor and the contralateral normal cortex (in parentheses) were 0.31 ± 0.22 (not detectable), 2.00 ± 0.53 (0.49 ± 0.07), 3.67 ± 0.36 (1.42 ± 0.22), and 7.23 ± 1.22 (3.64 ± 0.51), respectively. The ¹³¹I- SIP(L19) uptake pattern correlated best with ¹⁸F-fluorocholine uptake (ż = 0.80, averaged ż-transformed Pearson correlation coefficient) and ¹⁸F-FET uptake (ż = 0.79) and least with ¹⁸F-FDG (ż = 0.37). Conclusion: One day after intravenous injection, ¹³¹I-SIP(L19) displayed a very high tumorto-cortex ratio, which may be used in the diagnostic work-up of brain tumor patients. Of the 3 investigated ¹⁸F tracers, ¹⁸F-fluorocholine and ¹⁸F-FET correlated better with the pattern of ¹³¹I-SIP(L19) uptake than did ¹⁸F-FDG. Whether this means that ¹⁸F-fluorocholine and ¹⁸F-FET are better suited than ¹⁸F-FDG to monitor antiangiogenic therapy should be investigated in future studies.