18F-FAZA PET/CT in the Preoperative Evaluation of NSCLC: Comparison with 18F-FDG and Immunohistochemistry.

PURPOSE: To assess the capability of 18F-FAZA PET/CT in identifying intratumoral hypoxic areas in early and locally advanced non-small cell lung cancer (NSCLC) patients and to compare 18FFAZA PET/CT with 18F-FDG PET/CT and histopathological biomarkers and to investigate whether the assessment of tumour to blood (T/B) and tumour to muscle (T/M) ratios provide comparable information regarding the hypoxic fractions of the tumour. MATERIALS AND METHODS: Seven patients with NSCLC were prospectively enrolled (3 men, 4 women; median age: 71 years; range 63-80). All patients underwent to 18F-FDG PET/CT and 18F-FAZA PET/CT before surgery. Maximum standardized uptake value (SUVmax) was used to evaluate 18FFDG PET/CT images, while 18F-FAZA PET/CT images have been interpreted by using tumour-toblood (T/B) and tumour-to-muscle (T/M) ratio. Surgery was performed in all patients; immunohistochemical analysis for hypoxia biomarkers was performed on histologic tumor samples. RESULTS: All lung lesions showed intense 18F-FDG uptake (mean SUVmax: 7.35; range: 2.35-25.20). A faint 18F-FAZA uptake was observed in 6/7 patients (T/B < 1.2) while significant uptake was present in the remaining 1/7 (T/B and T/M=2.24). On both 2 and 4 h imaging after injection, no differences were observed between T/M and T/B (p=0.5), suggesting that both blood and muscle are equivalent in estimating the background activity for image analysis. Immunohisotchemical analysis showed low or absent staining for hypoxia biomarkers in 3 patients (CA-IX and GLUT-1: 0%; HIF-1α: mean 3.3%; range 0-10). Two patients showed staining for HIF-1α of 5%, with CA-IX being 60% and 30%, respectively and GLUT-1 being 30% and 80%, respectively; in 1/7 HIF-1α was 10%, CA-IX was 50% and GLUT-1 was 90%. In one patient a higher percentage of HIF-1α and CA-IX (20% and 70%, respectively) positive cells was present, with GLUT-1 being 30%. CONCLUSIONS: To the best of our knowledge, this is the first paper assessing hypoxia and glucose metabolism in comparison with immunohistochemistry in patients candidate to surgery for NSCLC. Although including a small number of patients, useful insight regarding correlation between imaging and immunohistochemistry are reported along with methodological suggestions for clinical practice.

Concomitant Lung Cancer and Gastrointestinal Stromal Tumor: First Report of Hypoxia Imaging With 18F-FAZA PET/CT.

A 76-year-old man underwent F-FDG PET/CT to complete staging and characterize a suspicious lung mass. Images showed intense uptake in the lung lesion and faint uptake in correspondence of a gastric mass, which was subsequently biopsied revealing a gastrointestinal stromal tumor. A F-FAZA PET/CT was also performed because of patient's enrollment in a prospective clinical trial (trial registration no. EudraCT 2011-002647-98), showing heterogeneous uptake of F-FAZA in the pulmonary lesion and faint uptake in correspondence of the gastrointestinal stromal tumor.

First Evaluation of PET-Based Human Biodistribution and Dosimetry of 18F-FAZA, a Tracer for Imaging Tumor Hypoxia.

18F-labeled fluoroazomycinarabinoside (18F-FAZA) is a PET biomarker for noninvasive identification of regional tumor hypoxia. The aim of the present phase I study was to evaluate the biodistribution and dosimetry of 18F-FAZA in non-small cell lung cancer patients. Methods: Five patients awaiting surgical resection of histologically proven or radiologically suspected non-small cell lung cancer were prospectively enrolled in the study. The patients underwent PET/CT after injection of 371 ± 32 MBq of 18F-FAZA. The protocol consisted of a 10-min dynamic acquisition of the heart to calculate the activity in blood, followed by 4 whole-body PET/CT scans, from the vertex to the mid thigh, at 10, 60, 120, and 240 min after injection. Urine samples were collected after each imaging session and at 360 min after injection. Volumes of interest were drawn around visually identifiable source organs to generate time-activity curves. Residence times were determined from time-activity curves, and effective doses to individual organs and the whole body were calculated using OLINDA/EXM 1.2 for the standard male and female phantoms. Results: Blood clearance was characterized by a rapid distribution followed by first-order elimination. The highest uptake was in muscle and liver, with respective percentage injected activity (%IA) peaks of 42.7 ± 5.3 %IA and 5.5 ± 0.6 %IA. The total urinary excretion was 15 %IA. The critical organ, with the highest absorbed radiation doses, was the urinary bladder wall, at 0.047 ± 0.008 and 0.067 ± 0.007 mGy/MBq for the 2- and 4-h voiding intervals, respectively. The effective doses for the standard male and female phantoms were 0.013 ± 0.004 and 0.014 ± 0.004 mSv/MBq, respectively, depending on the voiding schedule. Conclusion: With respect to the available literature, the biodistribution of 18F-FAZA in humans appeared to be slightly different from that in mice, with a low clearance in humans. Therefore, use of animal data may moderately underestimate radiation doses to organs in humans. Our dosimetry data showed that a 370-MBq injection of 18F-FAZA is safe for clinical use, similar to other widely used PET ligands. In particular, the effective dose is not appreciably different from those obtained with other hypoxia tracers, such as 18F-fluoromisonidazole.