Abscopal Effect After SIRT: It Exists, but How Could We Use It?
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COMMENTARY
COMMENTARY
Abscopal Effect After SIRT: It Exists, but How Could We Use It? Julien Edeline1
•
Yan Rolland2 • Etienne Garin3
Received: 26 August 2020 / Accepted: 2 September 2020 Springer Science+Business Media, LLC, part of Springer Nature and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) 2020
In this volume of CVIR, Powerski et al. present an interesting article studying the incidence of the abscopal effect (AE) following radioembolization (also known as Selective Internal Radiation Therapy or SIRT) of liver metastases [1]. The AE is a rare occurrence following external beam radiotherapy (EBRT). It has been described since the 1950s as the shrinkage of tumors outside of the radiation field, frequently occurring a few weeks or months after delivery of EBRT. This rare event has recently gained much interest, with the documentation of an immunological mechanism supporting it, and with the advent of immunooncology. Indeed, the potential for a synergistic effect between EBRT and immunotherapy led to great expectations, and a number of clinical trials were launched… currently, results are still awaited and the promises are not yet met [2]. Mechanisms underlying the AE are now better described [3]. Radiotherapy induces immunogenic cell death, leading to better recognition of the tumor cells by the immune system. Moreover, radiotherapy can stimulate the production of cytokines (like interferon-beta) that could stimulate & Julien Edeline [email protected] Yan Rolland [email protected] Etienne Garin [email protected] 1
Medical Oncology, Centre Euge`ne Marquis, av bataille Flandres Dunkerque, 35042 Rennes, France
2
Interventional Radiology, Centre Euge`ne Marquis, Rennes, France
3
Nuclear Medicine, Centre Euge`ne Marquis, Rennes, France
anticancer immune response, as well as the upregulation of MHC (major histocompatibility complex) class I. Another potential interesting interaction between radiotherapy and immunotherapy is the upregulation of PD-L1 (programmed death-ligand 1) following radiotherapy, which could be an escape mechanism but also an opportunity for combination. However, the overall effect of radiotherapy on the immune microenvironment is complex, and clearly depends on the context and on the radiotherapy regimen used. Indeed, the dose and fractionation used was shown to have a major impact for the potential of AE [4]. This was, to our knowledge, only studied in the context of EBRT. How the protracted delivery of SIRT, which is very different from EBRT from a radiobiological perspective, will also have potential for AE was uncertain. Powerski et al. thus did an important work, trying to elucidate whether AE could arise following SIRT. They applied a stringent methodology to assure that the shrinkage seen was not related to bilateral SIRT or by concomitant systemic treatment, which explain the attrition in the number of studied patients. Their main result confirms what is known after EBRT: AE can appear, but only at a very lo
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