头颈部肿瘤（HNC）是一组上呼吸道-消化道肿瘤的异质性肿瘤，全球新增病例达931,922例，死亡病例达467,125例。其中约90%为鳞状细胞来源（HNSCC）。HNSCC与过度吸烟、饮酒以及感染致癌病毒有关。在现代肿瘤学中，通过基因分型肿瘤组织以指导临床决策已成为常见实践，但在HNSCC患者管理中，细胞病理学或组织病理学仍然是诊断和治疗规划的主流。由于肿瘤异质性以及由于其解剖位置而无法获取肿瘤组织的问题，迫切需要寻找替代方法来评估肿瘤活动。液体活检方法可以克服肿瘤异质性的问题，该问题与对小组织活检进行分析有关。此外，液体活检提供了重复活检采样，甚至对于有访问限制的肿瘤患者也适用。液体活检是指在体液中发现的生物标志物，通常为血液，可以进行样本采集，提供患者以及其潜在恶性肿瘤的临床有价值信息。迄今为止，大多数液体活检研究集中在基于血液的生物标志物上，如循环肿瘤DNA（ctDNA）、循环肿瘤细胞（CTCs）和循环微RNA。在本综述中，我们将重点关注ctDNA作为HNSCC的生物标志物，因为它具有稳定性，在多种体液中存在，适应现有的临床实验室技术平台，并且采集和运输容易。我们将讨论ctDNA释放入循环的机制，ctDNA分析中的技术进展，ctDNA作为HNSCC管理中的生物标志物，以及将ctDNA转化为临床应用的一些挑战和未来展望。ctDNA为HNSCC预后和疾病监测提供了一种最小侵入性的方法，并将为个体化医学铺平道路，从而显著改善结果并降低医疗成本。© 2023 中华民国国家科学委员会。

Head and Neck cancers (HNC) are a heterogeneous group of upper aero-digestive tract cancer and account for 931,922 new cases and 467,125 deaths worldwide. About 90% of these cancers are of squamous cell origin (HNSCC). HNSCC is associated with excessive tobacco and alcohol consumption and infection with oncogenic viruses. Genotyping tumour tissue to guide clinical decision-making is becoming common practice in modern oncology, but in the management of patients with HNSCC, cytopathology or histopathology of tumour tissue remains the mainstream for diagnosis and treatment planning. Due to tumour heterogeneity and the lack of access to tumour due to its anatomical location, alternative methods to evaluate tumour activities are urgently needed. Liquid biopsy approaches can overcome issues such as tumour heterogeneity, which is associated with the analysis of small tissue biopsy. In addition, liquid biopsy offers repeat biopsy sampling, even for patients with tumours with access limitations. Liquid biopsy refers to biomarkers found in body fluids, traditionally blood, that can be sampled to provide clinically valuable information on both the patient and their underlying malignancy. To date, the majority of liquid biopsy research has focused on blood-based biomarkers, such as circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), and circulating microRNA. In this review, we will focus on ctDNA as a biomarker in HNSCC because of its robustness, its presence in many body fluids, adaptability to existing clinical laboratory-based technology platforms, and ease of collection and transportation. We will discuss mechanisms of ctDNA release into circulation, technological advances in the analysis of ctDNA, ctDNA as a biomarker in HNSCC management, and some of the challenges associated with translating ctDNA into clinical and future perspectives. ctDNA provides a minimally invasive method for HNSCC prognosis and disease surveillance and will pave the way in the future for personalized medicine, thereby significantly improving outcomes and reducing healthcare costs.© 2023. National Science Council of the Republic of China (Taiwan).