Radiobiological Principles of Radiotherapy for Benign Diseases

Abstract

Inflammatory degenerative and benign hyperproliferative diseases arise from complex and pathologically unbalanced multicellular interactions and altered microenvironmental conditions. Low and intermediate doses of ionizing radiation are clinically reported to ameliorate these disorders, but the understanding of the basis for the therapeutic effects is still at an early state. In recent years, however, it has become obvious by experimental in vitro and in vivo studies that a variety of cellular and osteoimmunological mechanisms were related to the anti-inflammatory, anti-degenerative, and antiproliferative efficacy of low-dose exposure. These mechanisms cover modulation of inflammatory properties of leukocytes, macrophages, fibroblasts, and endothelial cells, secretion of cytokines and growth factors, and impact on osteoclast and osteoblast activation. Notably, these mechanisms display comparable dose-effect relationships with a maximum effect in the range between 0.3 and 0.7 Gy, empirically identified to be most effective in the treatment of inflammatory degenerative disorders. In this chapter, we aim to summarize current findings and models exploring the mechanisms underlying the immunomodulatory and antiproliferative properties of low- and intermediate-dose radiotherapy for benign disorders.