title: Failure patterns relative to radiation treatment fields for stage II-IV thymoma.
abstract: BACKGROUND
  The optimal radiation therapy (RT) field design for thymomas remains unclear. Here we report the failure patterns in stage II-IV thymoma after RT at two tertiary referral centers, classified according to the new International Thymic Malignancy Interest Group definitions.
  
  
  METHODS
  We reviewed 156 stage II-IV patients with thymoma treated with definitive (n=24) or adjuvant (n=132) RT. All RT was delivered without elective nodal irradiation (median dose 5040 cGy). Intrathoracic failures were classified as (1) in-field failures (within 100% isodose line [IDL]), (2) marginal recurrences (<100% and ≥50% IDL), and (3) out-of-field failures (outside the 50% IDL).
  
  
  RESULTS
  The median follow-up was 61 months. Surgical margins were positive in 39%. The median tumor size was 9 cm. The 5-year cumulative incidence of all intrathoracic failures was 24% (n=34). Failures occurred within the RT field (n=5), marginally (n=1), out-of-field (n=22), and synchronously in- and out-of-field (n=6). The 5-year cumulative incidence of in-field failures was 7%. These were associated with Masaoka stage and tumor size. Macroscopically positive margins were associated with more local failures. Intrathoracic failures occurred most commonly in the pleural space (n=29) and lymph nodes (n=9). Patients with more advanced stage, and those treated with intensity-modulated radiation therapy had more intrathoracic failures. RT dose and chemotherapy did not impact failure patterns.
  
  
  CONCLUSIONS
  Although there were few in-field failures in patients who received RT for stage II-IV thymomas, a high rate of out-of-field intrathoracic failures still occurred. Further study is necessary to identify treatment approaches that prevent pleural recurrences.
authors: Departments of *Radiation Oncology, †Thoracic Surgery, ‡Thoracic Oncology, §Pathology, ¶Epidemiology and Biostatistics, and ‖Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York; Departments of #Radiation Oncology and **Thoracic Surgery, The University of Texas MD Anderson Cancer Center, Houston, Texas; and ††Department of Radiation Oncology, Mt. Sinai Medical Center, New York, New York.
authors: Andreas
authors: A
authors: Rimner
authors: Daniel R
authors: DR
authors: Gomez
authors: Abraham J
authors: AJ
authors: Wu
authors: Weiji
authors: W
authors: Shi
authors: Ellen D
authors: ED
authors: Yorke
authors: Andre L
authors: AL
authors: Moreira
authors: David
authors: D
authors: Rice
authors: Ritsuko
authors: R
authors: Komaki
authors: Kenneth E
authors: KE
authors: Rosenzweig
authors: Gregory J
authors: GJ
authors: Riely
authors: James
authors: J
authors: Huang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012189:Retrospective Studies; D013945:Thymoma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D013953:Thymus Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D017211:Treatment Failure; D055815:Young Adult