Liquid biopsies in thyroid cancers: a systematic review and meta-analysis

Thyroid cancer (TC) represents the most common endocrine malignant tumor. Liquid biopsy has been suggested as a new and accurate biomarker in cancer. This systematic review analyzes the existing literature on circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), cell-free DNA integrity index (cfDI), and their potential as biomarkers for TC, including the subtypes: differentiated (papillary and follicular), medullary, and anaplastic. A systematic search was performed in PubMed, Embase, and Cochrane databases for published articles in English between 1 January 1970 and 6 September 2022 (PROSPERO: CRD42022358592). The literature search generated a total of 635 articles. In total, 36 articles were included (patients = 2566). Four studies reported that higher levels of CTCs were associated with metastases and worse prognosis. Nineteen studies found the presence of mutated ctDNA in TC patients. The diagnostic accuracy in detecting BRAFV600E as ctDNA was determined in 11 studies regarding papillary TC. The pooled sensitivity, specificity, and diagnostic odds ratio were estimated at 56% (95% CI 36-74), 91% (95% CI 84-95) and 12 (95% CI 4.09-33.11), respectively. Four studies concluded that the cfDI was higher in patients with TC compared to benign thyroid lesions and healthy controls. The detection of CTCs, ctDNA, and cfDI may have a potential prognostic value in TC in relation to diagnosis, disease progression, and treatment efficacy. Despite the promising potential of CTCs, ctDNA, and cfDI in TC management, limitations hinder direct comparison and generalization of findings. Standardized methodologies, larger patient cohorts, and a consensus on relevant markers are needed to validate their clinical applicability and enhance TC management.