A nutritional supplement containing fish oil and selenium has been identifiedthat potentiates radiotherapy of tumors ina synergistic fashion. Cotherapy with such a supplement and radiotherapyresults in substantially improved reductions in tumor volumeof animal models relative to radiotherapy alone, and reduces common sideeffects such as weight loss, inflammation, and damage to thegastrointestinal tract. Such cotherapy was also found to reduce the incidenceof metastasis from the primary implantation site, and tomodulate expression of genes associated with apoptosis in tumor cells. Aformulation for such a supplement that is both well toleratedand palatable is also provided.
