title: Role of adjuvant postoperative external beam radiotherapy for well differentiated thyroid cancer.
abstract: OBJECTIVE
  To analyze the outcome of adjuvant postoperative external beam radiotherapy (EBRT) in well-differentiated thyroid cancer (WDTC).
  
  
  METHODS
  We identified 84 patients treated with EBRT for WDTC from February 1981 to December 2010. Among them, we analyzed 39 patients who received EBRT after initial radical surgery. Twenty-four females and 15 males were included. The median age was 49 years (range, 16 to 72 years). There were 34 papillary thyroid carcinomas and 5 follicular thyroid carcinomas. Most patients showed pathologic T3/T4 stage (54%/26%). Ten patients (25.6%) had gross residual tumors. Five patients (12.8%) had tumor cells at the margin. The median EBRT dose and fraction size were 62.6 Gy and 1.8 to 2.0 Gy, respectively.
  
  
  RESULTS
  The median follow-up was 73 months (range, 21 to 372 months). The five-year overall survival (OS) and locoregional recurrence free survival (LRFS) were 97.4% and 86.9%, respectively. Locoregional failures occurred in 5 and all failure sites were the neck node area. In univariate analysis, OS was significantly influenced by invasion of the trachea (p = 0.016) or esophagus (p = 0.006). LRFS was significantly decreased by male (p = 0.020), gross residuum after resection (p = 0.002), close or positive tumor at surgical margin involvement (p = 0.044), and tracheal invasion (p = 0.040). No significant prognostic factor was identified in the multivariate analysis. No patient experienced the Radiation Therapy Oncology Group grade 3 or more toxicity.
  
  
  CONCLUSIONS
  Our locoregional control rate of 87.2% is comparable to historical controls with surgery alone, even though our study had a large proportion of advanced stage. Adjuvant EBRT may an effective and safe treatment option in patients with WDTC.
authors.affiliation: Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jeanny
authors.initials: J
authors.lastname: Kwon
authors.forename: Hong-Gyun
authors.initials: HG
authors.lastname: Wu
authors.forename: Yeo-Kyu
authors.initials: YK
authors.lastname: Youn
authors.forename: Kyu Eun
authors.initials: KE
authors.lastname: Lee
authors.forename: Kwang Hyun
authors.initials: KH
authors.lastname: Kim
authors.forename: Do Joon
authors.initials: DJ
authors.lastname: Park
keywords: Adjuvant; Follicular thyroid cancer; Papillary thyroid cancer; Radiotherapy