Measurement of Tumor Hypoxia in Patients with Locally Advanced Cervical Cancer using Positron Emission Tomography (PET) with 18F-Fluoroazomyin Arabinoside (18F-FAZA)

Publication date: Available online 2 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Kathy Han, Tina Shek, Douglass Vines, Brandon Driscoll, Anthony Fyles, David Jaffray, Harald Keller, Ur Metser, Melania Pintilie, Jason Xie, Ivan Yeung, Michael Milosevic
PurposePoor tumor oxygenation (hypoxia) is associated with inferior survival in cervical cancer and resistance to radiotherapy. Positron emission tomography (PET) imaging of tumor hypoxia is minimally invasive and allows evaluation of the entire tumor, but has not been widely studied in cervical cancer. This study assesses cervical tumor hypoxia using hypoxia tracer ¹⁸F-fluoroazomycin arabinoside (¹⁸F-FAZA), and compares different reference tissues and thresholds for quantifying tumor hypoxia.Methods and MaterialsTwenty-seven patients with cervical cancer were studied prospectively by PET imaging with ¹⁸F-FAZA before starting standard chemoradiation. The hypoxic volume (HV) was defined as all voxels within a tumor (T) with standardized uptake values (SUVs) greater than 3 standard deviations from the mean gluteus maximus muscle SUV value (M), or SUVs greater than 1–1.4 times the mean SUV value of the left ventricle, a blood (B) surrogate. The hypoxic fraction (HF) was defined as the ratio of the number of hypoxic voxels to the total number of tumor voxels.ResultsA ¹⁸F-FAZA PET HV could be identified in the majority of cervical tumors (89% when using T/M or T/B >1.2 as threshold) on the 2-hour static scan. The HF ranged from 0-99% (median 31%) when defined using the T/M threshold, and 0-78% (median 32%) with the T/B >1.2 threshold. HVs derived from the different thresholds were highly correlated (Spearman's correlation coefficient ρ between T/M and T/B >1–1.4 were 0.82-0.91), as were HFs (0.75-0.85). Compartmental analysis of the dynamic scans showed k3, the FAZA accumulation constant, to be strongly correlated with HF defined using the T/M (Spearman's ρ=0.72) and T/B >1.2 thresholds (0.76).ConclusionsHypoxia was detected in the majority of cervical tumors on ¹⁸F-FAZA-PET imaging. The extent of hypoxia varied markedly between tumors, but not significantly with different reference tissues/thresholds.



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