Pretreatment and midtreatment measurement of oxygen tension levels in headand neck cancers

Objective: Considerable evidence exists to suggest that tumor hypoxia resul ts in radioresistance, Historically, it has been difficult to assess tumor oxygen tension levels reliably. These levels can now be assessed in head an d neck malignancies using the Eppendorf pO(2) histograph, which uses a fine -needle electrode and a computerized micromanipulator, This technology was used to compare the pretreatment tumor oxygen tension level in lymph node m etastases of patients with head and neck cancer to measurements taken durin g nonsurgical treatment after a partial response had been achieved. Study D esign: Prospective study. Methods: Oxygen tension levels were measured in t he cervical lymph nodes of 10 patients with biopsy-proven head and neck squ amous cell carcinoma and cervical metastases who were being treated with no nsurgical management. These levels were obtained using the Eppendorf pO(2) histograph system. Measurements were taken before the start of treatment an d were repeated when the size of the cervical metastatic node had decreased by 50%. Normal subcutaneous tissue was measured during the same session, T he mean and median pO2 levels, as well as the percentage of measurements wi th pO(2) less than 5 mm Hg were determined, Results: A mean of 72.6 measure ments per session was taken from each lymph node. The median tumor pO(2) me asurement fell from a mean (+/-SD) of 13.9 +/- 8.0 mm Hg to 7.3 +/- 9.9 mm Hg, Even more dramatic, however, was the substantial increase in the percen tage of values less than 5 mm Hg, a rise from 29% to 52%. Conclusions: Whil e there is variability both in the pretreatment oxygenation of head and nec k cervical metastases and in the change in tumor oxygen tension during trea tment, there appears to be a decrease in the overall oxygenation of the tum ors, The dramatic increase in very low oxygen measurements may reflect sele ctive survival of radioresistant or chemoresistant hypoxic tumor cells, Cel ls at the very low level would be expected to be radiobiologically hypoxic (resistant to radiation-induced cell kill).