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Published on: May 4, 2011
Oxygen tension measurements of head and neck cancers
1Division of Otolaryngology/Head and Neck Surgery, University Medical Center, Stanford, Calif.
Objective:
There is continued investigation of agents capable of overcoming hypoxic cell radioresistance. The evaluation of tumor oxygenation, therefore, assumes great importance. Previous efforts to measure tumor oxygen tension (PO2) using polarographic methods were limited by the size of the electrodes and efficiency of measurements. A new system employing fine-needle electrodes and a computerized micromanipulator was evaluated.
Design:
Prospective study.
Patients:
Sixteen patients with cancers of the head and neck, seen at Stanford (Calif) University Medical Center and Santa Clara Valley Medical Center, San Jose, Calif, between March 1, 1991, and July 31, 1991. Of the 16 tumors, 14 were squamous cell carcinomas; 11 were previously untreated. In two patients, measurements were repeated during radiation therapy. In three patients, measurements were taken under conditions of varied inspired oxygen during anesthesia. In seven patients, subcutaneous tissue (SQ) measurements were made for comparison.
Results:
The mean (+/- SD) PO2 of all tumors was 25.6 +/- 20.2 mm Hg, with a range of 2.3 to 76.4 mm Hg. When only squamous cell carcinomas were considered, the mean tumor PO2 was 22.7 +/- 16.0 mm Hg. The mean SQ measurement was 57.2 +/- 12.8 mm Hg. In all cases (seven of seven) in which SQ data were available, the tumor PO2 was lower than the SQ PO2 by an average of 41.8 mm Hg. The mean tumor PO2 increased in two of three cases of hyperoxia and decreased in the the third. The mean tumor PO2 increased in one patient after 25 Gy of radiotherapy and remained the same in the other.
Conclusions:
These measurements suggest that there is significant interindividual variability in the PO2 of head and neck cancers. Squamous cell cancers are generally less well oxygenated than normal SQ tissue. The PO2 histograph identified patients with a low mean tumor PO2.
Insights
New fine-needle electrodes accurately measure tumor oxygen tension (PO2) in head and neck cancers. Results show significant variability and lower oxygen levels in tumors compared to normal tissue, aiding patient selection for therapies targeting hypoxic cells.
Area of Science:
- Oncology
- Medical Physics
- Radiation Oncology
Background:
- Hypoxic cells in tumors contribute to radioresistance, necessitating methods to evaluate tumor oxygenation.
- Previous polarographic methods for measuring tumor oxygen tension (PO2) had limitations in electrode size and measurement efficiency.
Purpose of the Study:
- To evaluate a new system using fine-needle electrodes and a computerized micromanipulator for measuring tumor PO2.
- To assess the impact of varied inspired oxygen and radiotherapy on tumor PO2.
Main Methods:
- Prospective study involving 16 patients with head and neck cancers.
- Measurements of tumor PO2 using fine-needle electrodes, with comparisons to subcutaneous tissue (SQ) PO2.
- PO2 measurements were taken under conditions of varied inspired oxygen and during radiation therapy in select patients.
Main Results:
- The mean tumor PO2 was 25.6 mm Hg, with significant interindividual variability (range 2.3–76.4 mm Hg).
- Squamous cell carcinomas showed a mean PO2 of 22.7 mm Hg, generally lower than SQ measurements (mean 57.2 mm Hg).
- Tumor PO2 increased with hyperoxia in 2/3 patients and showed varied responses to radiotherapy.
Conclusions:
- Head and neck cancers exhibit substantial interindividual variability in PO2.
- Squamous cell carcinomas are typically less oxygenated than normal subcutaneous tissue.
- PO2 measurements can identify patients with low tumor oxygenation, potentially guiding treatment strategies.
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