Abscopal Effect: A Rare Phenomenon During Radio-Immunotherapy

Abstract

Abscopal effect (ab scopus meaning away from the target) is defined as the effect that occurs where radiotherapy at one particular region of tumour would lead to the shrinkage of metastatic cancer at distant sites that were not irradiated, along with the irradiated site. The mechanism of the Abscopal effect involves the immune system, and researchers have been studying this phenomenon to understand the underlying molecular mechanism involved. In this review, we discuss the mechanism of the abscopal effect, its relationship to radiotherapy and immunotherapy, and how combining both radio- and immunotherapy increases the frequency of the phenomenon. Apart from radio and immunotherapy, surgical resection has also demonstrated an abscopal effect. We have also highlighted a few case reports and clinical studies that have been published previously. Lastly, the predictors of abscopal effect have also been discussed. Since this phenomenon is rare, it is hard to predict which patients will benefit and which patients will not benefit from this phenomenon.