Abscopal Effect Following Radiation Therapy in Cancer Patients: A New Look from the Immunological Point of View

Abstract

Abscopal effect, a radiobiology term meaning "away from target", was practically unheard of just ten years ago. This effect describes the elimination and cure of a non-treated tumor when another part of the body is irradiated. Successful treatment of cancer in patients with multiple metastatic foci has sporadically been reported. Abscopal effect after radiotherapy has been introduced as the key factor which induced an anticancer response in these metastatic lesions. Moreover, not receiving chemotherapy is reported to have a role in cancer regression after radiotherapy. Given this consideration, it can be hypothesized that standard radiotherapy doses, which usually classified as high-dose, may cause cancer cells to expose or release their sequestered antigens that had been previously masked. Furthermore, radiotherapy can decrease the suppressive effect of regulatory T cells which usually down modulate immune responses against cancers. Moreover, some data show that low dose total-body irradiation (TBI) alone (without standard localized high dose radiotherapy) may cause suppression of distant metastasis of tumor cells. Induction of a "whole body abscopal effect" can be involved in suppression of distant metastasis. Here we discuss whether cancer treatments could be more successful if immune system is boosted, not destroyed by the treatments such as chemotherapy.

Keywords: Cancer; Immune System; Radiobiology; Radiotherapy.