Methods of treating a malignant solid tumor in a patient in need thereof are provided, the methods including administering to the patient a combination therapy comprising: fractionated radiation therapy and a therapeutically effective amount of saposin C (SapC) and dioleoylphosphatidylserine (SapC-DOPS), wherein the fractionated radiation therapy includes a plurality of radiation fractions, each of said fractions delivering a radiation dose lower than a dose effective to inhibit tumor growth when administered alone. Also provided are methods of enhancing anti-tumor efficacy of SapC-DOPS.
