title: Prognostic stratification of thymic epithelial tumors based on both Masaoka-Koga stage and WHO classification systems.
abstract: BACKGROUND
  The aims of this study were to stratify the risk of recurrence based on the Masaoka-Koga stage and World Health Organization (WHO) classification systems after R0-resection for thymic epithelial tumors (TETs).
  
  
  METHODS
  A retrospective analysis was conducted on 479 patients who underwent surgery between Jan 1994 and Feb 2014 for TETs. The study group comprised 251 males and 228 females, with a median age of 52 years (range, 15-84 years).
  
  
  RESULTS
  Of the 479 patients, 406 (84.8%) patients underwent R0-resection. Recurrence after R0-resection occurred in 32 patients during a median follow-up of 53 months (range, 2-227 months). A multivariate analysis revealed that the preoperative treatment including chemotherapy (P=0.036), Masaoka-Koga stage (P=0.011) and the WHO classification (P=0.001) were predictors for recurrence after R0-resection. Patients were stratified into four risk groups using a potential model incorporating both the Masaoka-Koga stage and WHO classifications. Group 1 comprised WHO types A/AB/B1 in stage I/II; Group 2 comprised WHO type A/AB/B1 in stage III or WHO type B2/B3 in stage I/II or WHO type C in stage I; Group 3 comprised Type B2/B3/C in stage III, or WHO type C in stage II/III; and Group 4 comprised WHO type B2/B3/C in stage IV. The 5-year freedom-from-recurrence (FFR) rates were 99.4% for group 1, 84.7% for group 2, 63.7% for group 3, and less than 44.4% for group 4 (P<0.001). In group 3, the rate of locoregional recurrence of patients treated with postoperative radiation therapy was lower than patients treated without postoperative radiation therapy (P=0.032).
  
  
  CONCLUSIONS
  A risk model incorporating both Masaoka-Koga stage and WHO classification systems may provide multi-faceted information about recurrence and adjuvant treatment after R0-resection of TETs.
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Geun Dong
authors.initials: GD
authors.lastname: Lee
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Hyeong Ryul
authors.initials: HR
authors.lastname: Kim
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Se Hoon
authors.initials: SH
authors.lastname: Choi
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Yong-Hee
authors.initials: YH
authors.lastname: Kim
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Dong Kwan
authors.initials: DK
authors.lastname: Kim
authors.affiliation: 1 Department of Thoracic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea ; 2 Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Seung-Il
authors.initials: SI
authors.lastname: Park
keywords: Thymoma; recurrence; surgery; thymic carcinoma