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Comparison of the comet assay and the oxygen microelectrode for measuring tumor oxygenation in head-and-neck cancer patients . PURPOSE To compare the Eppendorf PO2 histograph and the alkaline comet assay as methods of measuring tumor hypoxia in patients with head-and-neck squamous cell carcinomas . MATERIALS AND METHODS As part of a larger clinical trial , 65 patients with head-and-neck squamous cell carcinoma nodal metastasis underwent tumor oxygenation measurements with Eppendorf PO2 histographs and comet assays , performed on fine-needle aspirates at 1 and 2 min after 5 Gy . Fifty-four patients had sufficient tumor cells for comet analysis at 1 min and 26 at both 1 and 2 min . Individual cells were examined for DNA single-strand breaks by alkaline gel electrophoresis , and the distribution of values was quantified using median tail moment ( MTM ) . Nonirradiated tumor cells from pretreatment fine-needle aspirates received 5 Gy in vitro to establish the oxygenated response . RESULTS There was a significant correlation between the 1- and 2-min MTM ( slope = 0.77 +/- 0.03 ) . There was no relationship between DNA damage in tumor cells irradiated in vitro and in vivo . No correlation was found between Eppendorf PO2 measurements and comet MTM . There was a statistically significant correlation between the treatment response in the node studied and comet MTMs , whereas no correlation was observed between treatment response and Eppendorf measurements . CONCLUSIONS Comet assays are reproducible , as shown by biopsies at 1 and 2 min . Intertumor variation in the MTM is not a result of intrinsic radiosensitivity but of tumor hypoxia . There was no correlation between Eppendorf PO2 measurements and comet MTM . Comet assays were better than Eppendorf in predicting treatment response as an end point for short-term outcome . Longer follow-up is needed to determine the role of the comet assay as a predictor for locoregional tumor control and survivals .
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Intervention_Other
Eppendorf PO2 histograph
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Intervention_Other
alkaline comet assay
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Intervention_Pharmacological
tumor oxygenation measurements with
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Intervention_Other
Eppendorf PO2 histographs
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Intervention_Pharmacological
and
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Intervention_Other
comet assays
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Intervention_Pharmacological
, performed on fine-needle aspirates at 1 and 2 min after 5 Gy
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Intervention_Pharmacological
5 Gy in vitro
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Outcome_Physical
tumor oxygenation
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Outcome_Physical
tumor hypoxia
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Outcome_Other
tumor oxygenation measurements with Eppendorf PO2 histographs and comet assays
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Outcome_Physical
DNA damage in tumor cells
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Outcome_Other
Eppendorf PO2 measurements and comet MTM
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Participant_Condition
head-and-neck cancer
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Participant_Condition
head-and-neck squamous cell carcinomas
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Participant_Sample-size
65 patients
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Participant_Condition
head-and-neck squamous cell carcinoma
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Participant_Sample-size
Fifty-four patients