Variations in tumour oxygen tension (pO2) during accelerated radiotherapy of head and neck carcinoma.

The study was performed to assess the effect of accelerated radiotherapy on oxygenation of primary tumours and metastatic nodes in patients with advanced head and neck tumours. In 14 patients with head and neck tumour, oxygen tension (pO2) was evaluated in normal tissues and tumours (primary tumour or metastatic neck node) before (0 Gy) and after 2 weeks (32 Gy) of accelerated radiotherapy (70 Gy in 3.5 weeks, with three daily fractions). Radiotherapy was combined with carbogen breathing in 5 patients. pO2 was measured using a polarographic technique. For pooled normal tissues, median pO2 was 38 mmHg before treatment and 46 mmHg after 2 weeks. For tumours, very low values (< 2 mmHg) represented 20% of the recorded values before treatment and 10% after 2 weeks. The relative increase in tumour oxygenation was more pronounced for primary tumours (median pO2 12 mmHg before treatment versus 26 mmHg after 2 weeks, P < 0.05) than for metastatic nodes (respectively, 20 and 27 mmHg P = 0.1). For the 5 patients who breathed carbogen during accelerated radiotherapy, the median pO2 was 44 mmHg at 2 weeks, compared with 13.5 mmHg before treatment (P = 0.05). Very low pO2 values, corresponding to tumour hypoxia, were found in the tumours (primary and metastatic neck nodes) prior to accelerated treatment. During the first 2 weeks of accelerated treatment, an increase in median pO2 was found in nine of the 14 tumours, together with a decrease in the frequency of very low values.

Tumor oxygenation after 1) carbogen and/or perflubron emulsion administration in tumor xenografts 2) carbogen administration in patients.

This study examines the changes in tumor pO2 distribution assessed by polarography (KIMOC 6650, Eppendorf) in 1) two human tumor xenografts after carbogen inhalation with or without a perflubron (perfluorooctylbromide) emulsion (Oxygent, Alliance Pharmaceutical corp.) and in 2) human head and neck carcinomas after carbogen inhalation. Mice bearing HRT18 or NA11+ tumors were restrained and their body temperature was kept constant. Perflubron emulsion (4 ml/kg) was injected i.v. in the mice. In patients, oxygenation of the head and neck metastatic lymph nodes was assessed before and/or during carbogen exposure. The distribution of pO2 values shifted upwards during carbogen exposure in both animals and patients while the proportion of low pO2 values decreased. The maximal effect was obtained with patients after 1 to 6 minutes of carbogen exposure, but 4 patients still maintained very low pO2s. Carbogen plus 4 ml/kg perflubron emulsion was more efficient than carbogen alone for increasing hypoxic tumor pO2 in animals. If the animals data could be extrapolated to humans, then the effect of carbogen on tumor oxygenation should be increased by perflubron emulsion administration.

Changes in the oxygenation of head and neck tumors during carbogen breathing.

The oxygenation of head and neck tumors and changes during carbogen breathing were assessed in 20 patients. The median oxygen tension (pO2) for each patient was lower in tumors before breathing carbogen than in normal tissues. The median pooled pO2 of all the tumors was 20 mmHg; for normal tissue it was 60 mmHg. Low values (below 10 mmHg) were found in 4 patients for the normal tissue and in 18 patients for tumors. During carbogen breathing, the median (61 mmHg) pO2 readings for all tumors was higher than that recorded before carbogen breathing. The frequency of low (< 10 mmHg) pO2 values decreased with carbogen breathing in 11 patients; only 4 patients still exhibited very low values (< 2 mmHg). Maximal effect was obtained within 1-6 min of gas exposure. The pO2 stayed high under carbogen breathing in 15 out of 16 patients. Return to pre-carbogen levels of oxygenation occurred in 1 min after the end of gas exposure. These data suggest that carbogen breathing increases tumor oxygenation as assessed by polarography. The breathing time appears to be important for therapeutical use and should to be taken into consideration.

Oxygenation of head and neck tumors.

BACKGROUND: Tumor hypoxia could play a role in the response to radiation therapy. Few data are available on oxygen tension (pO2) measurements in head and neck tumors. METHODS: The KIMOC-6650 Histograph (Eppendorf, Hamburg, Germany) was used to measure the oxygenation status of normal tissues and head and neck tumors in 20 patients. RESULTS: The median pO2 for normal tissues was 43 mmHg with very low pO2 values (2.0 mmHg or less) recorded in two patients. Low median pO2 levels (10 mmHg or less) were recorded in 2 of 5 primary tumors and in 11 of 15 metastatic lymphadenopathies, with very low values in 11 nodes. The median pO2 in tumors was lower than that of normal tissues in 12 of 15 patients with comparative measurements. Oxygen tension was recorded in three nodes after an evaluation of tissue density (by computed tomographic scanner); in two nodes, the mean and median pO2 values were lower in the hypodense areas than in isodense areas. The data for N2 and N3 nodes showed significantly more values below 2.0 mmHg as nodal size increased (P < 10(-4), by chi-square test). No systematic decrease in pO2 was recorded from the periphery to the center of the tumors. CONCLUSIONS: Very low pO2 values, corresponding to radiobiologic hypoxia, were found in most of these tumors. The prognostic value of these pO2 measurements in regard to treatment response remains to be demonstrated.