Preoperative and Postoperative Risk Stratification of Thyroid Papillary Microcarcinoma: A Comparative Study Between Kuma Criteria and 2015 American Thyroid Association Guidelines Risk Stratification

Abstract

Background: The incidence of micropapillary thyroid carcinoma (mPTC) has increased in the last decade. Active surveillance (AS) has been proposed as an alternative management for low-risk mPTC based on preoperative Kuma criteria. Controversy still exists on how to appropriately manage this group of patients, as some low-risk mPTC may harbor some postoperative features associated with disease recurrence as described in the 2015 American Thyroid Association (ATA) guidelines. Methods: We retrospectively reviewed 108 patients with histopathologic diagnosis of mPTC after surgery at a third level hospital in Mexico City from 2000 to 2018. Demographic and clinicopathologic data were analyzed as predictors for disease recurrence and/or metastatic disease (lymph node or distant). Comparison between group stratification based on preoperative Kuma criteria and postoperative 2015 ATA guidelines risk criteria for disease recurrence was performed. Measures of diagnostic accuracy were obtained for preoperative risk features according to the Kuma criteria. Results: Of 108 patients, 79 (73%) were classified as preoperative high-risk mPTC and 29 (27%) as low risk based on the Kuma criteria. Of these 79 high-risk patients, 38 (48%) were reclassified as low risk for disease recurrence, 12 (15%) as intermediate risk, and 29 (37%) remained as high risk based on the 2015 ATA risk criteria. Of the 29 preoperative low-risk patients, 19 (65.5%) remained as postoperative low risk for disease recurrence, 2 (7%) as intermediate risk, and 8 (27.5%) as high risk. Higher accuracy of preoperative risk features was obtained for lymph node and distant metastases, 84.2% and 97.2%, respectively. After multivariate analysis, age <40 years and microscopic extrathyroidal extension (ETE) were associated with higher risk for metastatic disease (lymph node or distant) in our cohort. Conclusions: Patients with mPTC under 40 years old and microscopic ETE are more prone to develop metastatic disease (lymph node or distant). One-third of our patients stratified as low-risk mPTC according to the Kuma criteria for AS had histopathologic features associated with a more aggressive clinical behavior or structural recurrence. In addition, lymph node and distant metastases are the preoperative risk features with the highest diagnostic accuracy for preoperative risk stratification.

Risk factors associated with preferential lateral lymph node metastasis in papillary thyroid carcinoma

“…Recently, researchers in Mexico compared the risk stratification between the Kuma criteria and the 2015 ATA guidelines. They reported that some patients who met the Kuma criteria required more aggressive management than active monitoring 23 . However, we disagree with the opinion that PTMC has been over‐treated.…”

Clinical and ultrasonic risk factors for high‐volume central lymph node metastasis in cN0 papillary thyroid microcarcinoma: A retrospective study and meta‐analysis

“…Patients with ETE have a lower 10‐year survival rate (75.2%) and disease‐specific survival rate (84.2%) 64 . Rafael et al 65 report that patients with PTMC having ETE are more likely to acquire metastatic illnesses (lymph node or distant). Similarly, cN0 PTMC patients with ETE showed a 2.84‐fold increase in the chance of developing hv‐CLNM as compared to those without ETE.…”

“…Patients with ETE have a lower 10-year survival rate (75.2%) and disease-specific survival rate (84.2%). 64 Rafael et al 65 66 Additionally, Xue et al 67 suggest that HT is protective against recurrence. However, Yin et al 68 show that HT is independently and positively linked to LNM in female PTMC patients aged <55 years.…”

Risk stratification of papillary thyroid microcarcinomas via an easy-to-use system based on tumor size and location: clinical and pathological correlations

“…As Miyauchi highlighted, low-risk PTMC refers to the absence of high-risk features, such as lymph node metastasis, extrathyroidal extension, FNA biopsy findings suggesting high-grade malignancy, growth progression, and location close to the recurrent laryngeal nerve [ 19 ]. Controversy still exists on how to appropriately manage this group of patients, as some PTMCs classified as low risk at the time of the initial surgery may later be associated with disease recurrence or with other features entailing a more aggressive behavior [ 20 ].…”