Radiotherapy is one of the main methods of local treatment of cancer. Related studies have found that radiotherapy radiation can induce a special immunostimulatory effect, namely abscopal effect (AE). Specifically, when irradiating local tumor lesions, the lesions outside the irradiated target area also shrink. carbon ion radiotherapy (CIRT) is currently the preferred method of clinical radiotherapy. Compared with conventional radiotherapy, it has more advantages and is considered to have the potential to activate tumor cells with stronger immunogenicity[1]。 First, from a physical point of view, carbon ions exhibit a characteristic energy distribution at depth, called "Bragg" peaks, with high levels of energy deposition in tissues close to the target; The proximal tissue receives very little energy. Secondly, from the biological point of view, carbon ions have higher energy transfer linear density (LET) and higher relative biological effects (RBE) than photons. The biological effects are at least 2~4 times larger than photon radiotherapy in the peak region[2,3,4]。 Due to the advantages of physical and biological properties of carbon ions, CIRT is considered to induce strong immune response more than conventional radiotherapy[5]。 Related studies have also shown that the mechanism of distant effect is believed to be that local radiotherapy triggers a series of changes in human immune system[6]。 There are few clinical and mechanistic studies on the distant effect induced by carbon ion radiotherapy. Most experimental results show that carbon ion radiotherapy can elicit strong pro-immune response and induce more obvious distant effect[5]。 This study summarized and reported three typical cases of distant effect since Wuwei carbon ion therapy system was officially put into clinical treatment, so as to provide a reference for the clinical study of distant effect produced by carbon ion radiotherapy.
