Prospective study and proposal of an outcome predictive nomogram in a consecutive prospective series of differentiated thyroid cancer based on the new ATA risk categories and TNM.

Introduction: The personalized management of differentiated thyroid cancer (DTC) is currently based on the postoperative TNM staging system and the ATA risk stratification system (RSS), both updated in 2018 and 2015, respectively. Purpose: We aimed to evaluate the impact of the last two editions of TNM and ATA RSS in the prediction of persistent/recurrent disease in a large series of DTC patients. Patients and methods: Our prospective study included 451 patients undergone thyroidectomy for DTC. We classified the patients according to TNM (both VIII and VII ed.) and stratified them according to the ATA RSS (both 2015 and 2009). We then evaluated the response to the initial therapy after 12-18 months according to the ATA "ongoing" risk stratification, and analyzed the variables associated with persistent/recurrent disease by multivariate analysis. Results: The performance of the last two ATA RSSs was not significantly different. By staging patients according to the VIII or VII TNM editions, we found significant differences only in the distribution of patients with structural disease classified in stages III and IV. At multivariate analysis, only T-status and N-status were independently associated with persistent/recurrent disease. Overall, ATA RSSs and TNMs showed low predictive power in terms of persistent/recurrent disease (by Harrell's test). Conclusions: In our series of DTC patients, the new ATA RSS as well as the VIII TNM staging provided no additional benefit compared to the previous editions. Moreover, the VIII TNM staging system may underestimate disease severity in patients with large and numerous lymph node metastases at diagnosis.

Is multifocality a risk factor in low-risk papillary thyroid cancer?

INTRODUCTION: Multifocality in papillary thyroid cancer (PTC) is a common event, ranging from 18% to 87%. Additional multiple foci are frequently very small and generally detected in pathology specimens. The mechanisms of intrathyroidal spread, and its correlation with age, gender, tumour size, and lymph node metastases remain unclear. Moreover, studies assessing the prognostic impact of PTC multifocality have yielded non-univocal results. We aimed to evaluate the following: a) the histopathological and clinical characteristics associated with multifocal PTC; and b) the impact of multifocality on the long-term outcome. MATERIAL AND METHODS: We analysed a consecutive series of 2814 PTC patients without evidence of microscopic extrathyroidal extension (T1a, T1b, and T2), all of whom had undergone total thyroidectomy and were followed-up (median 4.7 years) in our thyroid clinic. Females comprised 81.3% and males 18.7% (F/M = 4.4/1), with a median age at diagnosis of 45.0 years. Patients were subdivided into 2 groups: 72.7% unifocal tumour and 27.3% multifocal tumour. Post-surgical radioiodine ablation (RAI) (30-100 mCi of 131-I) was performed in 1425 (50.6%) patients. All patients were periodically followed with thyroglobulin and anti-thyroglobulin antibodies measurements and with neck ultrasonography under L-thyroxine therapy and subjected to additional radioiodine administration or another therapeutic measure if not cured. RESULTS: Patients in the multifocal group were older (median age 46.4 vs. 44.5 years, respectively, p < 0.05) and presented a lower F/M ratio (F/M = 3.7/1 and 4.7/1; p = 0.01). T1a and T1b tumours showed no significant difference in multifocality rate whereas T2 tumours were less frequently multifocal (14.2% vs. 10.9%, p < 0.05). Multifocal tumours were more frequent in N1b (11.3% vs. 7.8%, p < 0.01) and less frequent in Nx (50.5% vs. 56.8%, p < 0.01), with no difference between the N0 and N1a groups. The clinical outcome was similar in the 2 group of patients (88.2 % in the unifocal group vs. 90.2% in the multifocal group). CONCLUSIONS: Multifocality is more frequent in older and male patients, in smaller tumours, and in N1b. However, multifocality "per se" was not associated, in our study, with worse clinical outcome in PTC patients.