Chemotherapy, Chemomodulation, and Immunomodulation of Radiation Therapy

Abstract

Radiation therapy can be modified by increasing the effectiveness of radiation on tumors (radiosensitizers), protecting normal tissues (radioprotectors), increasing oxygen concentration, or by using systemic therapy drugs. Radioprotectors are described by their dose reduction factor (DRF) while radiosensitizers are described by their enhancement ratio (ER). Both numbers are a ratio of radiation doses required to achieve a biological effect. Systemic agents can be classified as hypoxic radiosensitizers, hypoxic cytotoxins, classic alkylators, platinum agents, antibiotics, antimetabolites, vinca alkaloids, taxanes, topoisomerase inhibitors, hormonal agents, monoclonal antibodies, small molecule inhibitors (usually tyrosine kinase inhibitors), and immunomodulators. Progress is also being made in the field of gene therapy, although this is not yet mainstream.