6 July 1999 Modification of tumor response by manipulation of tumor oxygenation
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Abstract
Photodynamic therapy (PDT) requires tissue oxygenation during light irradiation. Tumor hypoxia, either pre-existing or induced by PDT during light irradiation, can severely hamper the effectiveness of a PDT treatment. Lowering the light irradiation does rate or fractionating a light dose may improve cell kill of PDT induced hypoxic cells, but will have no effects on pre-existing hypoxic cells. In the current study, we used hyper-oxygenation during PDT to overcome cell hypoxia in PDT. C3H mice with transplanted mammary carcinoma tumor were injected with 12.5 mg/kg Photofrin and irradiated with 630 nm laser light 24 hours later. Tumor oxygenation was manipulated by subjecting the animals to 3 a.t.p. hyperbaric oxygen or normobaric oxygen during PDT light irradiation. The results show a significant improvement in tumor response when PDT was delivered during hyper-oxygenation. With hyper-oxygenation, up to 80% of treated tumors showed no re-growth after 60 days. In comparison, only 20% of tumors treated while animals breathed normal room air, did not re-grow. To quantitatively evaluate the effects of manipulating tumor oxygenation, tumor p02 was measured with microelectrodes positioned in pre-existing hypoxic regions before and during the PDT light irradiation. The results show that hyper-oxygenation may oxygenate pre-existing hypoxic cells and compensate oxygen depletion induced by PDT light irradiation. In conclusion, hyper-oxygenation may provide effective ways to improve PDT treatment efficiency by oxygenating both pre-existing and treatment induced cell hypoxia.
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Qun Chen, Qun Chen, Jill Beckers, Jill Beckers, Fred W. Hetzel, Fred W. Hetzel, } "Modification of tumor response by manipulation of tumor oxygenation", Proc. SPIE 3592, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VIII, (6 July 1999); doi: 10.1117/12.351506; https://doi.org/10.1117/12.351506
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