BACKGROUND: Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor from parafollicular cells that produce calcitonin (Ct). Despite several existing guidelines for the surgical management of sporadic MTC (sMTC), optimal initial surgical management of the thyroid, the central and the lateral neck remains a matter of debate.
METHODS: A systematic review in PubMed and Scopus for current guidelines addressing the surgical management of sMTC and its referenced citations was conducted as per the PRISMA guidelines.
RESULTS: Two-hundred and one articles were identified, of which 7 met the inclusion criteria. Overall, guidelines vary significantly in their recommendations for the surgical management of sMTC. Only one guideline recommended partial thyroidectomy for limited disease, but the possibility to avoid completion thyroidectomy in selected cases is acknowledged in 42% (3/7) of the remaining guidelines. The majority of guidelines (71.4%; 5/7) recommended prophylactic central neck dissection (CND) for all patients while the remaining two guidelines recommended CND based on Ct level and tumor size. The role of prophylactic lateral neck dissection based on preoperative Ct levels was recommended by 42% (3/7) of guidelines. Overall, these guidelines are based on low-quality evidence, mostly single-center retrospective series, some of which are over 20 years old.
CONCLUSIONS: Current surgical management guidelines of sMTC should be revised, and ought to be based on updated data challenging current recommendations, which are based on historic, low-quality evidence. Partial thyroidectomy may become a viable option for small, limited tumors. Prospective, multi-center studies may be useful to conclude whether prophylactic ND is necessary in all sMTC patients.

Little is known about nationwide practice patterns for the management medullary thyroid cancer (MTC) in relation to the 2015 American Thyroid Association guidelines and their impact on survival.
Using the Surveillance, Epidemiology, and End Results Program database (2000-2018), MTC treatment patterns were evaluated in terms of adherence to the 2015 American Thyroid Association guidelines across three time periods (2000-2009, 2010-2015, and 2016-2018). Outcomes of interest were guideline concordance, treatment utilization trends, disease-specific survival (DSS), and overall survival (OS).
A total of 3332 patients with MTC were identified. Of which, 53.8%, 33.2%, and 11.4% of patients had localized, regional, and distant disease, respectively. In patients with locoregional disease, the rate of guideline-concordant surgery improved over time from 63.0% in 2000-2009 to 76.0% in 2016-2018 (P < 0.001). Guideline-concordant care was associated with increased OS (HR = 1.85, 95% CI: 1.42-2.43, P < 0.001) in patients with localized disease and increased DSS (HR = 1.65, 95% CI: 1.01-2.54, P < 0.001) and OS (HR = 1.89, 95% CI: 1.35-2.58, P < 0.001) in patients with regional disease. The median OS and DSS in patients with distant disease were 31 and 55 mo, respectively, and the rate of chemotherapy use rose from 21.6% to 39.2% (P = 0.003).
The rate of guideline-concordant surgery for locoregional MTC increased after guideline publication in 2015, with an observed prolongment in OS and DSS. Chemotherapy use among patients with distant disease has increased over time, but their prognosis remains variable.