title: Does the T1 subdivision correlate with the risk of recurrence of papillary thyroid cancer?
abstract: BACKGROUND
  Based on the AJCC seventh TNM classification, T1 intraglandular tumors are subdivided into T1a (≤10 mm) and T1b (11-20 mm), but the differences in prognosis remain controversial. The present study aimed to determine the clinicopathological features and outcomes of T1a and T1b patients.
  
  
  METHODS
  A retrospective study of 2518 T1 patients, including 1840 T1a (73 %) and 678 (27 %) T1b patients who underwent surgery for PTC from 1978 to 2014, was conducted. In patients with a preoperative or operative diagnosis of PTC, a total thyroidectomy (TT) with prophylactic (macroscopically N0) or therapeutic (evident N1) lymph node dissection (LND) was performed. Other patients had a TT or partial thyroidectomy without LND. The mean follow-up time was 8.9 ± 8.8 years (median, 6.5 years; range, 1-36.4 years).
  
  
  RESULTS
  A TT was performed in 2273 patients (90 %), including 1184 (52 %) with LND. Other patients (n = 245) had a single lobectomy with isthmectomy. Multifocality, bilaterality, number of tumors, sum of the largest size of all foci, vascular invasion, and (in patients with LND) LN metastases were significantly more frequent in T1b than in T1a patients. Of the 1184 patients with LND, 278 had LN metastases (N1, 23 %), including 136/680 T1a (20 %) and 142/504 (28 %) T1b patients (p = 0.002). These LN metastases were diagnosed after a prophylactic LND in 86/609 T1a (14 %) and 93/440 T1b (21 %) patients (p = 0.001). Recurrences were more frequent in T1b (n = 26, 3.8 %) than in T1a patients (n = 35, 1.9 %, p = 0.005). In the multivariate analysis, independent prognostic factors for recurrence in both groups were the number of tumors, the sum of the largest size of all foci and, in patients who had LND, LN metastases and extranodal extension. For N0-x patients, the recurrence rate was significantly higher in the T1b than in the T1a group (2.4 vs. 0.9 %, respectively, p = 0.005), although this rate was similar in N1 patients (16.2 % for T1a and 9.2 % for T1b patients, p = 0.1). The 5-year disease-free survival rates for T1a and T1b patients were 98.3 and 96.6 %, respectively (p = 0.01).
  
  
  CONCLUSIONS
  For PTC patients, T1b had poorer clinicopathological features and increased risk of recurrence than T1a.
authors.affiliation: Departments of General and Endocrine Surgery, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Chereau
authors.affiliation: Departments of General and Endocrine Surgery, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Trésallet
authors.affiliation: Departments of General and Endocrine Surgery, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Severine
authors.initials: S
authors.lastname: Noullet
authors.affiliation: Departments of General and Endocrine Surgery, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Gaelle
authors.initials: G
authors.lastname: Godiris-Petit
authors.affiliation: Departments of Pathology, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Tissier
authors.affiliation: Departments of Nuclear Medicine, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Leenhardt
authors.affiliation: Departments of General and Endocrine Surgery, Hospital Pitié Salpêtrière, APHP, University Pierre and Marie Curie (Paris VI), Paris, France. fabrice.menegaux@aphp.fr.|Service de Chirurgie Générale, Hôpital de la Pitie Salpêtrière, 47-83 Boulevard de l'hôpital, 75651 Cedex 13, Paris, France. fabrice.menegaux@aphp.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Menegaux
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D002291:Carcinoma, Papillary; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000209:etiology*; D009367:Neoplasm Staging; D012189:Retrospective Studies; D012306:Risk; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D013965:Thyroidectomy; D055815:Young Adult
keywords: Lymph node dissection; Lymph node metastases; Papillary; Recurrence; Thyroid cancer; Thyroidectomy