A method for measuring differential blood oxygen saturation in a solid tumor is described that includes the steps of obtaining a first oxygenation image of a solid tumor before, during, or immediately after a administration of vascular therapy; obtaining a second oxygenation image of the solid tumor after a devascularization time period; and determining a differential blood oxygen saturation value by comparing the first oxygenation image and the second oxygenation image. The differential blood oxygen saturation value can be compared to a blood oxygen saturation necrosis value to provide a prognosis for tumor recurrence, or to guide of the tumor.