Comparative Study On Current Selective Criteria Of Low-risk PTMC Cases For Active Surveillance

Objective: The incidence of papillary thyroid micro-carcinoma(PTMC)is increasing dramatically.Nowadays,low-risk PTMC is defined by different standards,such as Kuma Hospital Standard,ATA Guideline Standard and CATO Standard.The aim of the present study is to identify the best method for preoperative risk classification of the actual low-risk PTMC patients who underwent operative management and try to provide informative data concerning active surveillance(AS)strategy for low-risk PTMC in our country.Methods: In this retrospective study,patients with PTMC who underwent thyroid surgery for the first time between 2014 and 2016 in our hospital were included.Patients were divided into low-risk group and high-risk group according to standards defined by Kuma Hospital Standard,ATA Guideline Standard and CATO Standard respectively.Then the actual post-operative conditions of PTMC patients were evaluated according to the clinicopathological characteristics after operation(actual low-risk group and actual high-risk group).Preoperative and postoperative risk data,postoperative clinicopathological characteristics and postoperative condition assessments were compared among these patients with PTMC.Results: The cohort consisted of 600 patients.Among them 517(86.1%)cases met the Kuma criteria for low-risk stratification,524(87.3%)met the ATA criteria for low-risk stratification,and only 41(6.8%)met the CATO criteria for low-risk stratification.In the low-risk group,303 cases(50.5%)did not need surgical treatment.In the aspect of age,the difference between Kuma low-risk group and high-risk group was significant(P=0.044,P=0.046),while the difference between CATO low-risk group and high-risk group was not significant(P=0.107).In terms of TSH level,there was significant difference between Kuma low-risk and high-risk groups(P=0.016),but there was no significant difference between the other two criteria(P=0.077,P=0.236).Additional clinical features(gender and family history of thyroid cancer)were not significantly different among the three low-risk/high-risk groups.In terms of the size of lesions indicated by preoperative ultrasound,the differences of lesion diameters of grade 4 and above and among the three low-risk/high-risk groups were significant.The lesions of low-risk group were smaller than those of high-risk group,while the differences of maximum diameter of lesions of grade 4 and above were significant between the low-risk/high-risk group of CATO(P=0.000);in terms of the number of lesions,the difference of Kuma low-risk/high-risk group and ATA low-risk group was significant(P=0.000).There were no significant differences between high-risk groups(P=0.087.P=0.115),but there was significant difference between low-risk and high-risk groups of CATO(P=0.000).There was significant difference in the location of lesions between Kuma low-risk/high-risk groups(P=0.000),but no significant difference was found between ATA low-risk/high-risk groups and CATO low-risk/high-risk groups(P=0.311,P=0.471).Preoperative ultrasound showed that there was significant difference between the Kuma low-risk/high-risk group and ATA low-risk/high-risk group(P=0.000),but there was no significant difference between CATO low-risk/high-risk group(P=0.543).There was significant difference in suspicious extrathyroidal invasion between Kuma low-risk and high-risk groups(P=0.000),but no significant difference was found between ATA low-risk/high-risk groups and CATO low-risk/high-risk groups(P=0.311,P=0.471).In the comparison of pathological characteristics and the evaluation of post-operative condition,in terms of maximum lesion size,lesion diameter and size,the low-risk group of all evaluation criteria was significantly lower than the high-risk group.In terms of the number of lesions and lymph node metastasis,there were significant differences between Kuma low-risk/high-risk group and ATA low-risk/high-risk group(P=0.005,P=0.002,P=0.000,P=0.000),while there was no significant difference between CATO low-risk/high-risk group(P=0.539 and P=0.114).In the aspect of combined thyroid diseases,there was significant difference between the Kuma low-risk/high-risk group and ATA low-risk/high-risk group(P=0.018,P=0.015),and there was no significant difference among other groups.There were significant differences in the post-operative condition assessment among the low-risk/high-risk groups(P=0.000,P=0.000,P=0.042).The actual condition evaluation after operation was compared between the low-risk group and the high-risk group.It was noted that the high-risk group of Kuma standard and ATA standard needed surgery.The low-risk group of CATO standard had the lowest proportion of patients requiring surgery,which was more suitable for identifying the low-risk PTMC population suitable for AS strategy.Univariate analysis indicated that the risk factors include age(< 45 years old),size of lesions,number of lesions(multiple lesions)in preoperative assessment items,lymph node metastasis and number of lesions(multiple lesions)in post-operative assessment items.The result of multivariate analysis revealed that the risk factors were lymph node metastasis and number of lesions(multiple lesions)in the post-operative assessment items.Conclusion: At present,while there may be a subset of patients for whom more aggressive therapy is indicated,many patients with PTMC may be over-treated.The high-risk PTMC population classified according to Kuma standard and ATA standard is more suitable for operative management,while the low-risk PTMC population classified according to CATO standard is seemly more suitable for AS strategy.Further improvement of research is still required.