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Background: The role of minimal extrathyroidal extension (mETE) as a risk factor for persistent papillary thyroid carcinoma (PTC) is still debated. The aim of this study was to assess the clinical impact of mETE as a predictor of worse initial treatment response in PTC patients and to verify the impact of radioiodine therapy after surgery in patients with mETE. Methods: We reviewed all records in the Italian Thyroid Cancer Observatory (ITCO) database and selected 2237 consecutive patients with PTC who satisfied the inclusion criteria (PTC with no lymph node metastases and at least 1 year of follow-up). For each case, we considered initial surgery, histological variant of PTC, tumor diameter, recurrence risk class according to the American Thyroid Association (ATA) risk stratification system, use of radioiodine therapy, and initial therapy response, as suggested by ATA guidelines. Results: At 1-year follow-up, 1831 patients (81.8%) had an excellent response, 296 (13.2%) had an indeterminate response, 55 (2.5%) had a biochemical incomplete response, and 55 (2.5%) had a structural incomplete response. Statistical analysis suggested that mETE (odds ratio [OR] 1.16, p=0.65), tumor size >2 cm (OR 1.45, p=0.34), aggressive PTC histology (OR 0.55, p=0.15), and age at diagnosis (OR 0.90, p=0.32) were not significant risk factors for a worse initial therapy response. When evaluating the combination of mETE, tumor size, and aggressive PTC histology, the presence of mETE with a >2 cm tumor was significantly associated with a worse outcome (OR 5.27, 95% CI, p=0.014). The role of radioiodine ablation in patients with mETE was also evaluated. When considering radioiodine treatment, propensity score-based matching was performed, and no significant differences were found between treated and non-treated patients (p=0.24). Conclusions: This study failed to show the prognostic value of mETE in predicting initial therapy response in a large cohort of PTC patients without lymph node metastases. The study suggests that the combination of tumor diameter and mETE can be used as a reliable prognostic factor for persistence and could be easily applied in clinical practice to manage PTC patients with low-to-intermediate risk of recurrent/persistent disease.

et al., [Context]: Individualized management, incorporating papillary thyroid cancer (PTC) variant-specific risk, is conceivably a useful treatment strategy for PTC, which awaits comprehensive data demonstrating differential risks of PTC variants to support. [Objective]: This study sought to establish the differential clinicopathological risk of major PTC variants: conventional PTC (CPTC), follicular-variant PTC (FVPTC), and tall-cell PTC (TCPTC). [Methods]: This was a retrospective study of clinicopathological outcomes of 6282 PTC patients (4799 females and 1483 males) from 26 centers and The Cancer Genome Atlas in 14 countries with a median age of 44 years (interquartile range, 33-56 y) and median follow-up time of 37 months (interquartile range, 15-82 mo)., [Results]: The cohort consisted of 4702 (74.8%) patients with CPTC, 1126 (17.9%) with FVPTC, and 239 (3.8%) with TCPTC. The prevalence of high-risk parameters was significantly different among the three variants, including extrathyroidal invasion, lymph node metastasis, stages III/IV, disease recurrence, mortality, and the use (need) of radioiodine treatment (all P < .001), being highest in TCPTC, lowest in FVPTC, and intermediate in CPTC, following an order of TCPTC > CPTC ≫ FVPTC. Recurrence and mortality in TCPTC, CPTC, and FVPTC were 27.3 and 6.7%, 16.1 and 2.5%, and 9.1 and 0.6%, corresponding to events per 1000 person-years (95% confidence interval [CI]) of 92.47 (64.66-132.26) and 24.61 (12.31-49.21), 34.46 (30.71-38.66), and 5.87 (4.37-7.88), and 24.73 (18.34-33.35) and 1.68 (0.54-5.21), respectively. Mortality hazard ratios of CPTC and TCPTC over FVPTC were 3.44 (95% CI, 1.07-11.11) and 14.96 (95% CI, 3.93-56.89), respectively. Kaplan-Meier survival analyses showed the best prognosis in FVPTC, worst in TCPTC, and intermediate in CPTC in disease recurrence-free probability and disease-specific patient survival. This was particularly the case in patients at least 45 years old. [Conclusion]: This large multicenter study demonstrates differential prognostic risks of the three major PTC variants and establishes a unique risk order of TCPTC > CPTC ≫ FVPTC, providing important clinical implications for specific variant-based management of PTC., This work was supported by the US National Institutes of Health (NIH) Grants No. RO1CA113507 and R01CA189224 (to M.X.). In addition, the studies at individual centers were supported as follows: National Science Centre Poland Grants No. N403 194340 and N N401 612440 to A.C. and B.J., respectively, and Milestone Grant No. 267398 to both (Poland); Grants from Queensland Government Smart State Fellowship and Griffith Health Institute to A.K.L. (Australia); Grants No. RD12/0036/0030 FIS-ISCIII, S2011/BMD-2328 TIRONET, and SAF2013-44709-R to P.So. (Spain); grants from Fondazione Cassa di Risparmio di Perugia and Associazione Italiana per la Ricerca sul Cancro (IG 9338) (Italy) and the Beadle Family Foundation (San Antonio, TX) to E.P.; Grant IGA MH CR NT 13901-4 to V.S. and B.B. (the Czech Republic); grants from the New South Wales Cancer Institute to C.J.O. and from Cancer Council of New South Wales to R.C.-B. (Australia); Italian Government-Ministero della Salute Grant No. RF-2011-02350857 to G.T. (Italy); Grant NIH/NIA 5R03AG042334-02 to L.Y. (United States); Grants from the Ministerodella Istruzione Universitaria e Ricerca Scientifica, the AssociazioneItaliana per la Ricerca sul Cancro, the Istituto Toscano Tumori, and the Ministero della Salute to D.V. and R.E (Italy); and Grant No. CB-2011-03-02 from the Korean Foundation for Cancer Research to Y.K.S. and T.Y.K. (South Korea); Research Grants 2012/02902-9 and 2013/03867-5 from The São Paulo State Research Foundation (FAPESP) to J.M.C. (G.O. is a FAPESP scholar and J.M.C. is a Brazilian Research Council investigator (Brazil); AIRC Grant No. IG 10316 to F.B. (Italy); Grant No. SHDC 12014229 from Shanghai Hospital Development Center to H.X. (China); Programa Operacional Regional do Norte (ON.2—O Novo Norte), under the Quadro de Referência Estratégico Nacional, and through the Fundo Europeu de Desenvolvimento Regional to M.S.-S. and P.So.