Abstract
Background and purpose: This was an investigation to study the effect of giving carbogen and nicotinamide (CON) on pO 2 and the radiation response of human xenografted tumours. Materials and methods: The human xenografts were two sarcomas (ENE2 and ES3) and a glioblastoma (HTZ17). Nicotinamide (500 mg/kg, i.p.) was administered 60 min before pO 2 measurements and irradiation, while carbogen was given for 5 min before and during these treatments. Tumour pO 2 was measured with an Eppendorf electrode and radiation response was assessed by local tumour control following irradiation with 10 daily fractions. Results: All three xenografts were found to be poorly oxygenated (about 80% of all pO 2 values were ≤2.5 mmHg). CON treatment improved the oxygenation status in all three tumours such that 65, 52 and 71% of the pO 2 values were ≤2.5 mmHg in ENE2, ES3 and HTZ17, respectively. However, only in ES3 was this decrease significant. The TCD 50 doses for all tumours were around 52–54 Gy. No significant improvement was seen with CON in ENE2 (TCD 50=48 Gy) and HTZ17 (TCD 50=56 Gy), but for the ES3 xenograft a significant decrease to 42 Gy was found. Conclusions: The three tumours used in this study appeared to show the same level of hypoxia as measured both by pO 2 and radiation response. However, only one tumour showed a significant improvement after CON treatment, suggesting that not all hypoxic human tumours might benefit from this type of therapy.
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