Accumulating evidence suggests that a high tumour burden has a negative effect on anticancer immunity. The concept of tumour burden, simply defined as the total amount of cancer in the body, in contrast to molecular tumour burden, is often poorly understood by the wider medical community; nonetheless, a possible role exists in defining the optimal treatment strategy for many patients. Historically, tumour burden has been assessed using imaging. In particular, CT scans have been used to evaluate both the number and size of metastases as well as the number of organs involved. These methods are now often complemented by metabolic tumour burden, measured using the more recently developed 2-deoxy-2-[¹⁸F]-fluoro-d-glucose (FDG)-PET/CT. Serum-based biomarkers, such as lactate dehydrogenase, can also reflect tumour burden and are often also correlated with a poor response to immune-checkpoint inhibitors. Other circulating markers (such as circulating free tumour DNA and/or circulating tumour cells) are also attracting research interest as surrogate markers of tumour burden. In this Review, we summarize evidence supporting the utility of tumour burden as a biomarker to guide the use of immune-checkpoint inhibitors. We also describe data and provide perspective on the various tools used for tumour burden assessment, with a particular emphasis on future therapeutic strategies that might address the issue of inferior outcomes among patients with cancer with a high tumour burden.

越来越多的证据表明，高肿瘤负荷对抗癌免疫有负面影响。肿瘤负荷的概念，简单地定义为体内癌症的总量，与分子肿瘤负荷相比，更广泛的医学界通常知之甚少；尽管如此，在为许多患者确定最佳治疗策略方面仍可能发挥作用。从历史上看，肿瘤负荷一直使用成像进行评估。特别是，CT 扫描已被用于评估转移的数量和大小以及涉及的器官数量。这些方法现在通常由代谢性肿瘤负荷补充，使用最近开发的 2-deoxy-2-[ ¹⁸ F]-fluoro - d-葡萄糖（FDG）-PET/CT。基于血清的生物标志物，例如乳酸脱氢酶，也可以反映肿瘤负荷，并且通常还与对免疫检查点抑制剂的不良反应相关。其他循环标志物（如循环游离肿瘤 DNA 和/或循环肿瘤细胞）作为肿瘤负荷的替代标志物也引起了研究兴趣。在这篇综述中，我们总结了支持肿瘤负荷作为生物标志物指导免疫检查点抑制剂使用的证据。我们还描述了用于评估肿瘤负荷的各种工具的数据并提供了观点，特别强调了未来可能解决高肿瘤负荷癌症患者预后较差问题的治疗策略。