PT - JOURNAL ARTICLE AU - Li, Xiao-Feng AU - Ma, Yuanyuan AU - Sun, Xiaorong AU - Humm, John L. AU - Ling, C. Clifton AU - O'Donoghue, Joseph A. TI - High <sup>18</sup>F-FDG Uptake in Microscopic Peritoneal Tumors Requires Physiologic Hypoxia AID - 10.2967/jnumed.109.071233 DP - 2010 Apr 01 TA - Journal of Nuclear Medicine PG - 632--638 VI - 51 IP - 4 4099 - http://jnm.snmjournals.org/content/51/4/632.short 4100 - http://jnm.snmjournals.org/content/51/4/632.full SO - J Nucl Med2010 Apr 01; 51 AB - The objective of this study was to examine 18F-FDG uptake in microscopic tumors grown intraperitoneally in nude mice and to relate this to physiologic hypoxia and glucose transporter-1 (GLUT-1) expression. Methods: Human colon cancer HT29 and HCT-8 cells were injected intraperitoneally into nude mice to generate disseminated tumors of varying sizes. After overnight fasting, animals, breathing either air or carbogen (95% O2 + 5% CO2), were intravenously administered 18F-FDG together with the hypoxia marker pimonidazole and cellular proliferation marker bromodeoxyuridine 1 h before sacrifice. Hoechst 33342, a perfusion marker, was administered 1 min before sacrifice. After sacrifice, the intratumoral distribution of 18F-FDG was assessed by digital autoradiography of frozen tissue sections. Intratumoral distribution was compared with the distributions of pimonidazole, GLUT-1 expression, bromodeoxyuridine, and Hoechst 33342 as visualized by immunofluorescent microscopy. Results: Small tumors (diameter, &lt;1 mm) had high 18F-FDG accumulation and were severely hypoxic, with high GLUT-1 expression. Larger tumors (diameter, 1–4 mm) generally had low 18F-FDG accumulation and were not significantly hypoxic, with low GLUT-1 expression. Carbogen breathing significantly decreased 18F-FDG accumulation and tumor hypoxia in microscopic tumors but had little effect on GLUT-1 expression. Conclusion: There was high 18F-FDG uptake in microscopic tumors that was spatially associated with physiologic hypoxia and high GLUT-1 expression. This enhanced uptake was abrogated by carbogen breathing, indicating that in the absence of physiologic hypoxia, high GLUT-1 expression, by itself, was insufficient to ensure high 18F-FDG uptake.