A wide range of cancer immunotherapy approaches has been developed including non-specific immune-stimulants such as cytokines, cancer vaccines, immune checkpoint inhibitors (ICIs), and adoptive T cell therapy. Among them, ICIs are the most commonly used and intensively studied. Since 2011, these drugs have received marketing authorisation for melanoma, lung, bladder, renal, and head and neck cancers, with remarkable and long-lasting treatment response in some patients. The novel mechanism of action of ICIs, with immune and T cell activation, leads to unusual patterns of response on imaging, with the advent of so-called pseudoprogression being more pronounced and frequently observed when compared to other anticancer therapies. Pseudoprogression, described in about 2-10% of patients treated with ICIs, corresponds to an increase of tumour burden and/or the appearance of new lesions due to infiltration by activated T cells before the disease responds to therapy. To overcome the limitation of response evaluation criteria in solid tumors (RECIST) to assess these specific changes, new imaging criteria-so-called immune-related response criteria and then immune-related RECIST (irRECIST)-were proposed. The major modification involved the inclusion of the measurements of new target lesions into disease assessments and the need for a 4-week re-assessment to confirm or not confirm progression. The RECIST working group introduced the new concept of "unconfirmed progression", into the irRECIST. This paper reviews current immunotherapeutic approaches and summarises radiologic criteria to evaluate new patterns of response to immunotherapy. Furthermore, imaging features of immunotherapy-related adverse events and available predictive biomarkers of response are presented.

中文翻译：

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肿瘤对免疫疗法反应的影像学。

已经开发了广泛的癌症免疫疗法方法，包括非特异性免疫刺激剂，例如细胞因子，癌症疫苗，免疫检查点抑制剂（ICI）和过继性T细胞疗法。其中，ICI是最常用和深入研究的。自2011年以来，这些药物已获得针对黑色素瘤，肺癌，膀胱癌，肾癌和头颈癌的上市许可，对某些患者的治疗效果显着且持久。ICI具有免疫和T细胞活化作用的新型作用机制，导致成像反应的异常模式，与其他抗癌疗法相比，所谓的伪进展的出现更为明显，且经常被观察到。伪进展，在大约2-10％的接受ICI治疗的患者中，对应于在疾病对治疗作出反应之前由于活化的T细胞浸润导致的肿瘤负荷增加和/或新病变的出现。为了克服实体瘤反应评估标准（RECIST）来评估这些特定变化的局限性，提出了新的成像标准，即所谓的免疫相关反应标准，然后是免疫相关RECIST（irRECIST）。重大修改涉及将新靶标病变的测量结果纳入疾病评估，并需要进行4周的重新评估以确认或不确认进展。RECIST工作组将新的“未经确认的进展”概念引入了irRECIST。本文回顾了当前的免疫治疗方法，并总结了放射学标准，以评估对免疫治疗反应的新模式。