Researches Of The Pertinent Issues Of Central Neck Dissection For Papillary Thyroid Carcinoma

Background:The value of prophylactic central neck dissection(CND)for clinically node-negative(cNO)papillary thyroid carcinoma(PTC)remains controversial.Though prophylactic CND can reduce postoperative thyroglobulin levels,provide complete staging of lymph nodes,and decrease the rate of regional recurrences reported in a few researches,there are insufficient evidences to confirm that prophylactic CND could decrease locoregional recurrence or improve disease-free survival of cNO PTC patients.What's more,prophylactic CND induced higher risk of recurrent laryngeal nerve injury and hypoparathyroidism compared with thyroidectomy alone,especially the incidence of transient hypoparathyroidism.In this study,we aimed to investigate the indication of prophylactic CND for cNO PTC and the method of in situ preservation of inferior parathyroid gland(IPTG)during CND for PTC.Objective:The purpose of this study was to investigate the indication of prophylactic CND for cNO PTC,and describe a new surgical concept of preserving IPTG in situ during CND for PTC.Methods:Part 1:611 consecutive patients with cNO PTC from January 2013 to December 2015 were retrospectively analyzed.Cervical lymph nodes were harvested and the number and size of central metastatic lymph nodes were measured.The incidence and risk factors of metastatic lymph nodes in the central compartment with more than 5 or>2 mm were investigated,which was defined as non-small-volume central lymph node metastases(NSVCLNM).Part 2:The study group consisted of 181 patients with primary PTC who underwent total thyroidectomy with CND using the new surgical concept "a layer of thymus-blood vessel-inferior parathyroid gland(TBP)",between January and December 2014.The control group included 306 patients with primary PTC who underwent conventional total thyroidectomy with CND between January 2012 and December 2013.The proportion of IPTGs preserved in situ and postoperative hypoparathyroidism rates in the two groups were compared.The incidence of transient and permanent hypoparathyroidism of 591 patients with primary PTC underwent total thyroidectomy with CND using the new surgical concept between January 2014 and June 2017 was investigated.Results:Part 1:NSVCLNM were detected in 67(11.0%)of 611 cNO PTC patients and 37(7.7%)of 478 cNO PTMC patients,respectively.Male gender,age<36 years,multifocal lesions,extrathyroidal extension,and tumor size>0.85cm were independent risk factors of NSVCLNM in cNO PTC patients.The sensitivity and specificity of having ?3 risk factors for predicting NSVCLNM in cNO PTC patients was 46.3%and 86.8%,respectively.Male gender,age<37 years,multifocal lesions,and tumor size>0.65cm were independent risk factors of NSVCLNM in cNO PTMC patients.The sensitivity and specificity of having ?3 risk factors for predicting NSVCLNM in cNO PTMC patients was 43.2%and 90.9%,respectively.Part 2:There were no significant differences between the study and control groups in sex,age,tumor size,multifocality,extrathyroidal extension,vocal cord palsy,and number of harvested and metastatic central lymph nodes.The rate of IPTG preservation in situ was significantly improved from 37.9%to 76.3%on the left side(P<0.001),and from 52.0%to 77.9%on the right side(P<0.001),in the study group compared with the control group.The rate of parathyroid excised inadvertently was significantly decreased from 15.7%to 5.5%(P=0.001),and the incidence of transient hypoparathyroidism decreased significantly from 35.0%to 7.2%(P<0.001).The incidence of transient hypoparathyroidism of 591 PTC patients was 12.4%,and no patient developed permanent hypoparathyroidism.Conclusions:Part 1:Prophylactic CND was suggested for cNO PTC patients with>3 risk factors of NSVCLNM,while immediately surgery and prophylactic CND was suggested for cNO PTMC patients with>3 risk factors of NSVCLNM.Part 2:The proposed surgical concept could greatly improve the rate of IPTG preservation in situ,efficiently decrease the incidence of transient postoperative hypoparathyroidism,and ensure the completeness of CND.