MTC accounts for an extremely small proportion of thyroid carcinoma and is a moderate malignant carcinoma, and for it is derived from C cells, its biological characteristics and malignant degree differ from other types of thyroid carcinoma derived from thyroid follicular cells. MTC is prone to recurrence after operation. In this study, the recurrence rate after MTC reached 23% (17/74), which was lower than the recurrence rate reported in the previous literature (44.1% -47.3%) [4-5].
In terms of general information, through univariate analysis, Zhang Zaixing et al [6] fund that gender (female) and age (≥45 years) were important factors affecting survival (recurrence, death, etc.) (P <0.05). Through multifactorial analysis, Hassan et al. [4] found that gender(male) was the poor prognostic factors (recurrence, death, etc.) of MTC patients (P <0.05). In this study, the recurrence group and the non- recurrence group were more often to be male and young (≤52.5 years old), and there was no statistical significance between gender, age and recurrence (P> 0.05). The conclusions obtained in this study are partially consistent and partially contradictory with the conclusions of the above studies, which are related to the different definitions of the ending of the three studies and the small number of cases.
MTC is derived from C cells that secrete calcitonin, so it has the characteristic expression of elevated calcitonin. Some studies have found that patients with MTC who still have elevated postoperative calcitonin were more prone to have cervical lymph node metastasis and recurrence [7]. Through multivariate analysis, Hassan et al. [4] found that MTC patient’s postoperative calcitonin doubling time less than two years and that the rate of increase in calcitonin value greater than 0.05 pg/ml/month were poor prognostic factors (P <0.05). A study through meta-analysis showed that procalcitonin can be used as a marker for postoperative follow-up monitoring of MTC patients to monitor recurrence [5]. In this study, single factor KM survival analysis showed: preoperative calcitonin> 565.8pg / ml, postoperative calcium Factors> 45.0 pg/ml are factors that affect the recurrence of MTC patients (P <0.05, see Table-1). Only 60 cases had preoperative calcitonin and only 70 cases had postoperative calcitonin, so they were not included in the multivariate analysis. The conclusion that there is statistical significance between the elevated calcitonin (or procalcitonin) and the recurrence of MTC patients is not new, and the specific values of calcitonin (or procalcitonin) that affect recurrence are not the same in each study. This is related to the limited number of cases enrolled in various studies, the large age span, and different test levels.
Starting from the ultrasonic features of medullary thyroid carcinoma, the research on exploring the relationship between MTC and cervical lymph node metastasis is relatively extensive, while there are relatively few studies on the relationship between preoperative ultrasonic features and recurrence of MTC. Studies have pointed out that in sporadic medullary thyroid carcinoma, single-factor chi-square analysis believes that patients with tumors> 15 mm, irregular morphology, sharp edges, and masses located under the capsule have a higher risk of lateral neck lymph node metastasis (P <0.05) [8]. The ultrasound characteristics of medullary thyroid carcinoma mass include the size, number, echo, composition, boundary, morphology, invasion of the capsule, aspect ratio, calcification, blood flow, etc. In this study, single factor KM analysis showed that the tumor> 40.0mm, capsular invasion, and abnormal cervical lymph nodes were the survival factors affecting the recurrence of MTC patients (P <0.05). These three factors represent the size of the tumor, the relationship with the surrounding adjacent tissues, and the status of the lymph nodes, which can be further applied to the preoperative T and N stages of MTC patients. Some studies have shown that T4 is a poor prognostic factor through multi-factor analysis [4], and some studies have shown that TNM staging is a factor affecting prognosis through single factor analysis [6]. The results of the multi-factor COX regression analysis in this study showed that abnormal cervical lymph node was the only independent risk factor affecting the recurrence of MTC patients. In addition, this study found that in the recurrence group and the non-recurrence group, the tumors were mostly characterized by solidity, low echo, clear boundaries, and calcification. There were no statistically significant differences between the ultrasound features such as the composition, echo, boundary, calcification and recurrence of MTC patients.
In this study, the results of univariate KM analysis showed that: tumor> 40.0 mm, capsular invasion, abnormal cervical lymph nodes, preoperative calcitonin> 565.8 pg/ml, postoperative calcitonin> 45.0 pg/ml are the effects factors of MTC recurrence (P <0.05). The results of multi-factor COX regression analysis showed that abnormal cervical lymph node(HR=5.368,95%CI1.063-27.104,P=0.042) is independent risk factors affecting the recurrence of MTC patients. MTC patients with abnormal cervical lymph nodes are more likely to relapse. Calcitonin was not included in the multivariate analysis, but to a certain extent, preoperative calcitonin>565.8pg/ml, postoperative calcitonin>45.0pg/ml can also indicate more likely to relapse.
In this study, a total of 74 patients with MTC, including 17 cases of recurrence during follow-up, 57 cases of non-recurrence, and 2 death cases were not included in the study. The conclusion of this study is that the ultrasound features can be used for preoperative T and N staging, but no factors related to recurrence have been found from other ultrasound features such as the composition, echo, boundary, and calcification. At the same time, the number of recurrence cases in this study did not reach half of the total number of cases, and the median survival time could not be obtained in the K-M survival analysis. The follow-up study can be continued in the future.