Abstract
Simple SummaryThe anatomical staging system for thyroid cancer only contains categories for lymph node compartments. The metastatic lymph node ratio (LNR), which is the ratio of metastasized lymph nodes to the total number of evaluated lymph nodes, is suggested as a quantitative evaluation tool for lymph node metastasis in patients with medullary thyroid cancer in this study. The initial stratification implemented in this study was helpful in predicting structural recurrence, and LNR was identified as a predictor of disease-free survival.The lymph node ratio (LNR) has been investigated as a prognostic factor in many different types of cancers, including differentiated thyroid cancer; however, reports regarding medullary thyroid cancer (MTC) are limited. Therefore, this study aims to evaluate LNR as a risk factor for structural recurrence in patients with MTC. Medical records of patients treated for MTC in a single tertiary center between 1995 and 2017 were retrospectively reviewed. LNR is defined as the number of metastatic lymph nodes or lymph node metastases (LNM) divided by the number of retrieved lymph nodes or lymph node yield (LNY). In the survival analysis, recurrence-free survival was defined as the time from the date of total thyroidectomy to recurrence or last follow-up. To identify risk factors influencing structural recurrence, univariable and multivariable Cox proportional hazard models were used. A total of 132 patients were enrolled. The mean age of study participants was 49.7 years, and 86 patients (65%) were women. Structural recurrence was identified in 39 patients at the end of the study period, and the median follow-up period was 8.7 years. In univariable analyses, gross extra thyroidal extension, N stage, postoperative serum calcitonin and carcinoembryonic antigen (CEA) levels, and LNR were significant (p < 0.05) predictors of structural recurrence. In multivariable analysis, postoperative serum calcitonin, postoperative serum CEA, and LNR were identified as a predictor of disease-free survival (p < 0.05). LNR can potentially predict structural recurrence as a quantitative evaluation tool for lymph node metastasis in patients with MTC.
Highlights
Medullary thyroid cancer (MTC) consists of thyroid parafollicular cells and has distinct biological features [1]
Structural recurrence was identified in 39 patients at the end of the study period, and the median follow-up period was 8.7 years (Table 1)
Extensive surgery involving total thyroidectomy with central lymph node dissection is recommended as the initial treatment for patients with MTC as the condition is refractory to most medical therapies [3,22]
Summary
Medullary thyroid cancer (MTC) consists of thyroid parafollicular cells and has distinct biological features [1]. Unlike the effects observed in differentiated thyroid cancer (DTC), thyroid-stimulating hormone suppression is not effective for MTC treatment because parafollicular cells do not have the thyroid-stimulating hormone receptor [2]. Postoperative evaluation for initial risk stratification 2 of 11 is crucial for predicting prognosis in patients with MTC [4]. According to the American Joint Committee on Cancer (AJCC), the lymph node stages in patienttosmwyiitshpMooTr C[3]a. RTehecrleafsosrief,iepdosatospfeorlaltoivwese:vpaNlu0a,tionnofeovr iidnietniaclerioskf sltorcaotirfiecgaitoionnails crucial lymph node meftoarsptaresdisi;ctpinNg1par,omgneotasisstainsipsattoielnetvsewl iVthI MorTVCI[I4]ly. Mph nodes; and pN1b, metastasis to the unilatAercacol,rdbiinlagtteorathl,eoArmcoernictaranlJaotienrtaCl onmecmkitotereroentrCoapnhcaerry(AngJCeCal),ltyhme lpyhmpnhodneosde stages [5]. The AJCC sintapgaintigenstsyswteitmh MoTnClyacroencltaasisnisfiecdataesgfoorliloeswsfo: rpNly0m, npohevnioddeencceoomf lpoacrotrmegeinontsa;l lymph previonuodsestmuedtiaesstahsaisv; epNat1team, mpetteadsttaosiqsutoanletvitealtVivIeolryVaIsIsleysms plyhmnpodhens;oadnedsptaNtu1bs,[m6–etastasis
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