Rise of oxygenation in cervical lymph node metastasis during the initial course of radiochemotherapy

It has been hypothesized that during radiation treatment a reoxygenation of hypoxic tumor tissue takes place. To test this hypothesis, we have investigated whether reoxygenation in lymph node metastases could be determined by invasive Po-2 measurements. Through a hypodermic needle inserted transcutaneously into tumor-positive lymph nodes, polarographic oxygen determinations were made in 18 patients with advanced squamous cell carcinomas of the oropharynx and hypopharynx. These measurements were performed before therapy and a week after the onset of radiotherapy or radiochemotherapy, respectively. Low Po-2 values before treatment (mean value of the patient's median was 12.6 mm Hg Po-2) and a mean hypoxic fraction (Po-2 < 5 mm Hg) of 39.6% indicated manifest tumor hypoxia. After 1 week of treatment, a significant increase in the median Po-2 (mean value of shift: 7.3 mm Hg) and a reduction in the hypoxic fraction (mean value of shift: 13.4% Po-2 < 5 mm Hg, P < 0.03) were observed after both radiotherapy and radiochemotherapy. Thus invasive Po-2 histography fulfills the requirements for a method to confirm tumor hypoxia in head and neck tumors. The results obtained indicate that reoxygenation occurs during the initial phases of radiotherapy and radiochemotherapy, and they will form the basis for future comparative investigations on the possible influence of hypoxic parameters on tumor responsiveness toward radiation and radiochemotherapy.