Carcinoid syndrome (CS), mostly associated with small intestinal neuroendocrine tumors (SI-NETs) or lung-related NETs, is characterized by symptoms related to hormonal secretion and long-term complications, including carcinoid heart disease (CHD), which is potentially life-threatening. In the early stages of the disease, symptoms are non-specific, which leads to delayed diagnoses. The availability of reliable tumor markers is crucial for a prompt diagnosis and proper management. This review summarizes available evidence on the role of 24 h urinary 5-hydroxyindolacetic acid (24u5HIAA), which is the urinary breakdown metabolite of serotonin, in the diagnosis/follow-up of NET-related CS, with a focus on its potential prognostic role, while eventually attempting to suggest a timeline for its measurement during the follow-up of NET patients. The use of 24u5HIAA is an established biomarker for the diagnosis of NETs with CS since it shows a sensibility and specificity of 100% and 85–90%, respectively. The downside of 24u5-HIAA is represented by the need for 24 h urine collection and the risk of confounding factors (foods and medication), which might lead to false positive/negative results. Moreover, 24u5HIAA is useful in the follow-up of NETs with CS since a shorter double time correlates to a higher risk of disease progression/disease-specific mortality. Furthermore, an elevation in 24u5-HIAA is correlated with a dismal prognosis because it is associated with an increased likelihood of CHD development and disease progression/mortality. Other potentially interesting biochemical markers have been proposed, including plasmatic 5HIAA, although further standardization and prospective studies are required to define their role in the management of NETs. Meanwhile, 24u5HIAA remains the most accurate CS biomarker.
类癌综合征主要与小肠神经内分泌肿瘤或肺相关神经内分泌肿瘤相关，其临床特征表现为激素分泌相关症状及长期并发症，包括可能危及生命的类癌心脏病。疾病早期症状缺乏特异性，常导致诊断延迟。可靠的肿瘤标志物对于及时诊断和规范治疗至关重要。本文综述了24小时尿5-羟吲哚乙酸（血清素尿液分解代谢产物）在神经内分泌肿瘤相关类癌综合征诊断及随访中的作用证据，重点探讨其潜在的预后价值，并尝试为神经内分泌肿瘤患者随访中的检测时机提供建议。24小时尿5-羟吲哚乙酸作为诊断类癌综合征的成熟生物标志物，其敏感性和特异性分别达到100%和85-90%。但该检测需收集24小时尿液，且存在食物药物等混杂因素导致假阳性/阴性结果的风险。在类癌综合征随访中，较短的倍增时间与疾病进展/特异性死亡率升高相关，而24小时尿5-羟吲哚乙酸水平升高则提示预后不良，因其与类癌心脏病发生风险增加及疾病进展/死亡率升高相关。血浆5-羟吲哚乙酸等其他潜在生物标志物虽具研究价值，但仍需进一步标准化和前瞻性研究以明确其临床作用。目前，24小时尿5-羟吲哚乙酸仍是类癌综合征最精准的生物标志物。
肿瘤(癌症)患者之家