Effect of hypoxic irradiation following hyperbaric oxygen therapy on mice implanted with Lewis lung cancer

Objective: To observe the effect of hypoxic irradiation following hyperbaric oxygen therapy on murine tumor tissue and normal tissue. Methods: C57BL/6 mice implanted with Lewis lung cancer were divided into five groups: the irradiation group, the hypoxic irradiation group (LO), the hyperbaric oxygen irradiation group (HBO), the hyperbaric oxygen plus hypoxic irradiation group (HBO + LO) and the control group. The experiment was started when the transplanted tumor reached 1.0-2.0 cm. A dose of 20 Gy 6 MeV electron beam of DT was used for irradiation. Two and half atmosphere pressure of hyperbaric oxygen was given for 100 minutes during therapy and a mixture of 10.5% oxygen and 89.5%N2 was provided for hypoxic irradiation. ECT γ images were taken 120 minutes after 99mTc-HL91 injection. Results: (1) The mean murine tumor growth rate in both HBO group and HBO + LO group delayed significantly than that in other groups. (2) The survival times of both LO group and HBO +LO group were significantly longer than those of other groups. These two groups showed almost the same effect in protecting normal tissues and prolonging lives. (3) The imaging agent radioactivity ratio of tumor to contralateral (TPA) tissues in both HBO and HBO +LO groups decreased significantly than that in other groups. And no difference in the therapeutic effect was found in these two groups. Conclusion: The hypoxic irradiation following hyperbaric oxygen therapy might achieve a radiation-enhancing effect on tumor cells and a protective effect on normal tissues