Purpose: To investigate the influence of different treatment modalities (radiotherapy, chemotherapy, and hyperthermia) on the oxygenation of human tumor xenografts and to correlate it with the tumoricidal effect we conducted this study.
Methods and materials: Human-derived head-and-neck squamous cell carcinoma xenografts (implanted in nude mice/nine groups of 10 mice) were treated with various treatment modalities and combinations of them (radiation with 5 x 2 or 10 x 2 Gy, hyperthermia at 41 degrees C or 41.8 degrees C, chemotherapy with ifosfamide [32 mg/kg] or cisplatin [2 mg/kg]). The tumor volume was evaluated 3 times per week until Day 60. Tumor pO(2) was measured at Day 1, 5, 8, and 12 with a polarographic pO(2) histograph.
Results: Within treatment time (maximum, 10 days) the median pO(2) increased in all groups (except the control group), concomitantly the fraction of measurements of pO(2) that were less than 10 mm Hg showed a constant decrease (p < or = 0.001). The highest difference between the median pO(2) values and the fraction of measurements of pO(2) that were less than 10 mm Hg at the start and 1 week after the end of therapy occurred in the groups with radiochemothermotherapy (triple-modality therapy; p< or = 0.001). At Day 60, the highest rate of complete remissions was observed in the triple-modality therapy groups.
Conclusion: Tumor oxygenation under a single or combined cancer treatment is correlated with treatment efficacy in terms of complete remissions at Day 60. The posttherapeutic fraction of measurements of pO(2) that were less than 10 mm Hg correlates even better with the long term tumor free survival than the median pO(2) values or the pretherapeutic fraction of measurements of pO(2) that were less than 10 mm Hg.