Radiosensitizing effect by increase of tumor pO_2 using Perfluorochemicals.

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It is believed that the presence of radiobiologically hypoxic cells in human tumors is the major limiting factors for the complete control of tumors by radiotherapy. Perfluorochemicals (PFC) are able to absorb a great amount of oxygen in a high pO_2 environment and rapidly releases oxygen when the environmental pO_2 is low.In the present study, the changes in transplanted tumor pO_2 and the radiosensitizing effects by treatment with PFC and Carbogen(95%O_2 + 5% CO_2) or combination od AGII were investigated. The TCD_<50> (50% Tumor Cure Dose) was modified by factors of 1.47 + 0.03(S.E.) by treating the animals with carbogen plus PFC. The dose modification factor (DMF) for the skin reaction was 1.15 + 0.12(S.E.) and then, Therapeutic Gain Factor (TGF) was 1.28 + 0.04.The data presented in this report clearly demonstrate that an i.v. injection of PFC with Carbogen breathing can significantly increase the response of tumors to X-rays as measured by tumor growth and tumor cure. The therapeutic gain obtained in this study for a single exposure was 1.28, whereas larger therapeutic gains than we obtained in the present study was also reported by other investigators.Angiotension II(AG II) also increased pO_2 in the central area especially. This may indicate that AG II is useful in a larger tumor having a lot of hypovascular portion. The Phase I and II of clinical trials of PFC for radiotherapy patients is in progress in several medical centers in USA and Japan.