The Confluence of Stereotactic Ablative Radiotherapy and Tumor Immunology

Abstract

Stereotactic radiation approaches are gaining more popularity for the treatment of intracranial as well as extracranial tumors in organs such as the liver and lung. Technology, rather than biology, is driving the rapid adoption of stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), in the clinic due to advances in precise positioning and targeting. Dramatic improvements in tumor control have been demonstrated; however, our knowledge of normal tissue biology response mechanisms to large fraction sizes is lacking. Herein, we will discuss how SABR can induce cellular expression of MHC I, adhesion molecules, costimulatory molecules, heat shock proteins, inflammatory mediators, immunomodulatory cytokines, and death receptors to enhance antitumor immune responses.

Changes of systemic immune response after stereotactic ablative radiotherapy (SABR) - first results of a prospective study in early lung cancer patients

“…21,22 The advantage of radiosurgery, such as that used in our study, is the delivery of very high doses of radiation in a relatively short time, only to the gross tumor surrounded by a very small margin of healthy tissue. This technique improves treatment tolerance and, at least in theory, significantly reduces the risk of a decreased immune response.…”

Abscopal Benefits of Localized Radiotherapy Depend on Activated T-cell Trafficking and Distribution between Metastatic Lesions

“…A particularly exciting development, hailed by the editors of Science as the scientific breakthrough of 2013 (5), is that novel immunotherapeutic strategies show remarkable responses in some patients, especially if combined with common cytotoxic agents. Radiotherapy and chemotherapeutic agents have been shown to substantially enhance tumorspecific immune responses in well-established tumors (4,(6)(7)(8)(9)(10)(11). The synergy between radiotherapy and immunotherapy stems from radiation-induced effects including (i) immunogenic cell death that locally exposes a wealth of tumor antigens and…”

Effect of Low Magnetic Field on Dose Distribution in the SABR Plans for Liver Cancer

“…In contrast to conventional radio therapy, which delivers low dose to a larger volume for a higher number of daily fractions, SABR is usually given as a single dose or up to five doses once a day with tumor ablation and maximal normal-tissue sparing. [2][3][4][5][6] Despite these advantages, it could lead a more severe damage compared to conventional therapy if the positioning error occurred.…”