Abscopal effect of radiotherapy: an old concept in a new era

The abscopal effect is a phenomenon that describes the systemic antitumor response that can occur as a result of a localized radiotherapy. Although sporadic cases of abscopal effect have been reported since 1960’s, the number of reported cases are significantly increasing in the immunotherapy era. Immunotherapy seems to enhance the immunogenic effects of radiotherapy, thus increasing systemic antitumor response. Although combination of radiotherapy and immunotherapy is a promising strategy in the treatment of metastatic cancers, many questions regarding the optimal treatment remain unanswered. Increasing number of ongoing studies will hopefully provide answers to these questions, enabling the utilization of this strategy in systemic anticancer treatment.