PTGS2 and neoplasm: The present studies demonstrating that COX-2 inhibitor blocks IR-mediated augmentation of experimental tumor growth are not only consistent with previous studies characterizing the role of this eicosanoid-generating enzyme in PAF-mediated systemic immunosuppression [4, 6, 8] they also provide the rationale for future studies testing the ability of COX-2 inhibitors to enhance the effectiveness of RT.