There is significant rationale for combining radiation therapy (RT) and immuno-oncology (IO) agents, but the optimal radiation parameters are unknown. This review summarizes key trials in the RT and IO space with a focus on RT dose. Very low RT doses solely modulate the tumor immune microenvironment, intermediate doses both modulate the tumor immune microenvironment and kill some fraction of tumor cells, and ablative doses eliminate the majority of target tumor cells and also possess immunomodulatory effects. Ablative RT doses may have high toxicity if targets are adjacent to radiosensitive normal organs. The majority of completed trials have been conducted in the setting of metastatic disease and direct RT to a single lesion with the goal of generating systemic antitumor immunity termed the abscopal effect. Unfortunately, reliable generation of an abscopal effect has proved elusive over a range of radiation doses. Newer trials are exploring the effects of delivering RT to all or most sites of metastatic disease, with dose personalization based on the number and location of lesions. Additional directions include testing RT and IO in earlier stages of disease, sometimes in further combination with chemotherapy and surgery, where lower doses of RT may still contribute substantially to pathologic responses.

结合放射治疗（RT）和免疫肿瘤学（IO）药物有重要的理由，但最佳放射参数尚不清楚。本综述总结了 RT 和 IO 领域的关键试验，重点是 RT 剂量。极低的RT剂量仅调节肿瘤免疫微环境，中等剂量既调节肿瘤免疫微环境又杀死部分肿瘤细胞，消融剂量消除大部分靶肿瘤细胞并具有免疫调节作用。如果靶标邻近放射敏感的正常器官，消融性放疗剂量可能具有高毒性。大多数已完成的试验都是在转移性疾病的背景下进行的，并将放疗直接应用于单个病灶，其目标是产生全身抗肿瘤免疫，称为“远隔效应。不幸的是，事实证明，在一定范围的辐射剂量下，远隔效应的可靠产生是难以捉摸的。较新的试验正在探索对所有或大多数转移性疾病部位进行放疗的效果，并根据病变的数量和位置进行个性化剂量。其他方向包括在疾病早期阶段测试 RT 和 IO，有时进一步与化疗和手术相结合，其中较低剂量的 RT 仍可能对病理反应做出重大贡献。