Increasing Oxygenation and Radiation Sensitivity following Photodynamic therapy with verteporfin in the RIF-1 tumor

摘要

The combination of verteporfin-based photodynamic therapy (PDT) with radiation therapy from an orthovoltage device has been examined in the radiation induced fibrosarcoma tumor model. PDT with verterporfin using a 3 hour delay between injection and the time of optical irradiation has been shown to cause a significant rise is overall tumor oxygenation. It was hypothesized that this mechanism arises from the reduced oxygen consumption from cells where the PDT has targeted the mitochondria and shut down cellular respiration. Tumor blood flow was measured and found to still be patent immediately following therapy. This increasing oxygenation was thought to provide an opportunity to increase the radiation sensitivity of the tumor immediately following PDT. When this type of treatment was combined with radiation therapy, a delay in the tumor regrowth time demonstrated that the combined effect was greater than additive. Further study of this phenomenon will provide a more complete mechanistic understanding of the effect and possibly provide a viable pre-treatment for radiation therapy of tumor that increases the therapeutic ratio. This effect could be used to either increase the radiation dose without increasing the side effects or decrease the dose needed for the same effect on the tumor.