Department of Radiation Oncology, Peking University Third Hospital, Beijing, China.
Front Immunol. 2021 Jan 25;11:612072. doi: 10.3389/fimmu.2020.612072. eCollection 2020.
Hypofractionated radiotherapy is external beam irradiation delivered at higher doses in fewer fractions than conventional standard radiotherapy, which can stimulate innate and adaptive immunity to enhance the body's immune response against cancer. The enhancement effect of hypofractionated irradiation to immune response has been widely investigated, which is considered an approach to expand the benefit of immunotherapy. Meanwhile, increasing evidence suggests that hypofractionated irradiation may induce or enhance the suppression of immune microenvironments. However, the suppressive effects of hypofractionated irradiation on immunomicroenvironment and the molecular mechanisms involved in these conditions are largely unknown. In this context, we summarized the immune mechanisms associated with hypofractionated irradiation, highlighted the advances in its immunosuppressive effect, and further discussed the potential mechanism behind this effect. In our opinion, besides its immunogenic activity, hypofractionated irradiation also triggers homeostatic immunosuppressive mechanisms that may counterbalance antitumor effects. And this may suggest that a combination with immunotherapy could possibly improve the curative potential of hypofractionated radiotherapy.
适形放疗是一种比传统标准放疗剂量更高、分割次数更少的外照射放疗方法，它可以刺激固有和适应性免疫，增强机体对癌症的免疫反应。适形放疗对免疫反应的增强作用已经得到了广泛的研究，被认为是扩大免疫治疗获益的一种方法。同时，越来越多的证据表明，适形放疗可能诱导或增强免疫微环境的抑制。然而，适形放疗对免疫微环境的抑制作用及其在这些情况下涉及的分子机制在很大程度上尚不清楚。在这种情况下，我们总结了与适形放疗相关的免疫机制，强调了其免疫抑制作用的研究进展，并进一步讨论了这种作用背后的潜在机制。我们认为，除了其免疫原性活性外，适形放疗还引发了维持性免疫抑制机制，可能会抵消抗肿瘤作用。这可能表明与免疫疗法联合使用可能会提高适形放疗的治疗潜力。
