Table 1 Advantages and disadvantages of the methods of assessing hypoxia
From: Targeting hypoxia in solid and haematological malignancies
Method | Advantages | Disadvantages |
|---|---|---|
Oxygen Electrodes | Around 100 measurements taken- good overview of area No major adverse effects | Surface lesions only Invasive No repeat measurements Cannot account for necrotic areas- will give discordant results Artifacts-excessive oxygen consumption Technically skilled user and inter-operator variability |
Phosphorescence quenching | Real time oxygenation information Readings are independent of tracer concentrations | Invasive technique Technically skilled user Early in development- limited availability |
Electron Paramagnetic Resonance oximetry | Implantable technology- repeated results. Can monitor effects of treatment Absolute pO2 readings | Invasive- needs a direct probe in situ Early in development- limited availability |
Endogenous markers | Not affected by the sampling time or microenvironment It can be correlated within the same sample against other markers of tumour hypoxia | Cell line specific Can be affected by metabolic factors that vary between cells |
Dynamic contrast-enhanced magnetic resonance imaging | Non-invasive Widely available Radiology departments familiar with method and equipped to perform and report imaging Can be repeated to monitor effects of treatment with relative accuracy | When administered IV mostly absorbed in liver/spleen. Amount in tumours often insufficient to get an accurate reading Cleared within days- limited time period for collecting data When administered into tumour can only read oxygen tension within that area of the tumour Readings significantly affected by temperature |
Blood-oxygen level dependent magnetic resonance imaging | Non-invasive Can detect changes in tumour hypoxia over time | Small movements can lead to poor images and artefact Not a direct measure of oxygenation and therefore independent variables can interfere with measurements |
Positron emission tomography imaging | Non-invasive Widely available Familiar method- clinicians and radiology departments used to dealing with images and results Repeated measurements possible Enables the visualization of the hypoxic status of the entire tumour in 3D image | Varying tracers used result in varying uptake levels and result in some discrimination between hypoxic levels Relatively short half life of tracer means it must be manufactured and imaged within several hours |
Pimonidazole | Non-invasive Good prognostic correlation | Limited availability Requires tumour biopsy after administration of Pimonidazole- tumour needs to be accessible Invasive |