The Effect of Carbogen Breathing on (18)F-FDG Uptake in Non-Small-Cell Lung Cancer

It has been reported that (18)F-FDG uptake is higher in hypoxic cancer cells than in well-oxygenated cells. We demonstrated that (18)F-FDG uptake in lung cancer would be affected by high concentration oxygen breathing. Methods. Overnight fasted non-small-cell lung cancer A549 subcutaneous (s.c.) xenografts bearing mice (n = 10) underwent (18)F-FDG micro-PET scans, animals breathed room air on day 1, and same animals breathed carbogen (95% O(2) + 5% CO(2)) on the subsequent day. In separated studies, autoradiography and immunohistochemical staining visualization of frozen section of A549 s.c. tumors were applied, and to compare between carbogen-breathing mice and those with air breathing, a combination of (18)F-FDG and hypoxia marker pimonidazole was injected 1 h before animal sacrifice, and (18)F-FDG accumulation was compared with pimonidazole binding and glucose transporter 1 (GLUT-1) expression. Results. PET studies revealed that tumor (18)F-FDG uptake was significantly decreased in carbogen-breathing mice than those with air breathing (P < 0.05). Ex vivo studies confirmed that carbogen breathing significantly decreased hypoxic fraction detected by pimonidazole staining, referring to GLUT-1 expression, and significantly decreased (18)F-FDG accumulation in tumors. Conclusions. High concentration of O(2) breathing during (18)F-FDG uptake phase significantly decreases (18)F-FDG uptake in non-small-cell lung cancer A549 xenografts growing in mice.