Abscopal Effect of Radiotherapy in the Immunotherapy Era: Systematic Review of Reported Cases.

Nergiz Dagoglu,Hale B Caglar,Sule Karaman,Ethem N Oral

doi:10.7759/cureus.4103

Abstract

Mounting evidence suggests that radiation stimulates the immune system and this contributes to the abscopal effect, which is defined as “response at a distance from the irradiated volume.” Though identified more than 50 years ago, the abscopal effect is revisited today. One rationale is that the abscopal effect is often observed with efficient immunotherapy. Here, we give an overview of the clinical data on the abscopal effect, generated by a combination of immunotherapy and radiotherapy (RT). Only papers that included RT in combination with immunotherapy were evaluated according to four main categories including RT parameters, sequencing of therapies, the definition of the abscopal effect, and patient selection. Twenty-four cases in 15 reports were reviewed. The results varied. Patient ages ranged from 24 to 74. RT dose (median total dose 18-58 Gy) varied. Biologically effective dose (BED) 10 was calculated to be a median 49.65 Gy (28-151 Gy). The time to a documented abscopal response ranged from less than a month to 12 months. The large variation concerning fractionation and sequencing of therapies indicates that these conflicting points need to be resolved, to generate for the abscopal effect to be clinically significant.

Highlights

BackgroundRadiotherapy (RT) has been used as an effective local treatment modality in cancer management for decades
As a result of this synergy, an effect is described at distant points, which is known as the abscopal effect
One theory behind this is the recent developments in immunotherapy as there is a growing consensus that it would be easier to obtain an abscopal effect with immunotherapies and immunomodulation

Summary

Introduction

BackgroundRadiotherapy (RT) has been used as an effective local treatment modality in cancer management for decades. As a result of this synergy, an effect is described at distant points, which is known as the abscopal effect. The origin of this term is a combination of the Latin root words “ab-", meaning “far,” and “-scopus,” meaning “target” [2]. This phenomenon was first described by Mole in 1953, it only recently garnered revived clinical attention [3]. One theory behind this is the recent developments in immunotherapy as there is a growing consensus that it would be easier to obtain an abscopal effect with immunotherapies and immunomodulation

Results

Discussion

Conclusion