Laser blood-flow measurements in malignant tumors during photodynamic therapy (PDT)--an experimental study

Laser blood-flow measurements were made on the tumor surface of 18 human oral cancer tumors growing on the shank of nude mice during and up to 6 h after photodynamic therapy (PDT) to detect changes in microcirculation. In eight animals, the same procedure was done without PDT. Simultaneously, the skin microcirculation in the contralateral leg was measured to detect systemically caused changes in microcirculation. Two days later, specimens of the tumor region were taken and analyzed histologically. Our results suggest a mainly direct effect of PDT on the tumor cells rather than tumor necrosis caused by decreased microcirculation.