The role of molecular genetics in the clinical management of sporadic medullary thyroid carcinoma: A systematic review.

BACKGROUND: The significant variation in the clinical behaviour of sporadic medullary thyroid carcinoma (sMTC) causes uncertainty when planning the management of these patients. Several tumour genetic and epigenetic markers have been described, but their clinical usefulness remains unclear. The aim of this review was to evaluate the evidence for the use of molecular genetic and epigenetic profiles in the risk stratification and management of sMTC. METHODS: MEDLINE and Embase databases were searched using the MeSH terms "medullary carcinoma", "epigenetics", "molecular genetics", "microRNAs"; and free text terms "medullary carcinoma", "sporadic medullary thyroid cancer", "sMTC", "RET", "RAS" and "miR". Articles containing less than ten subjects, not focussing on sMTC, or not reporting clinical outcomes were excluded. Risk of bias was assessed using a modified version of the Newcastle-Ottawa Scale. RESULTS: Twenty-three studies met the inclusion criteria, and key findings were summarized in themes according to the genetic and epigenetic markers studied. There is good evidence that somatic RET mutations predict higher rates of lymph node metastasis and persistent disease, and worse survival. There are also several good quality studies demonstrating associations between certain epigenetic markers such as tumour miR-183 and miR-375 expression and higher rates of lymph node and distant metastasis, and worse survival. CONCLUSIONS: There is a growing body of evidence that tumour genetic and epigenetic profiles can be used to risk stratify patients with sMTC. Further research should focus on the clinical applicability of these findings by investigating the possibility of tailoring management to an individual's tumour mutation profile.