title: Adjuvant external beam radiation for medullary thyroid carcinoma.
abstract: BACKGROUND
  Adjuvant radiation is rarely used to treat medullary thyroid carcinoma (MTC). We hypothesized that external beam radiation therapy (EBRT) would improve overall survival (OS) in MTC patients.
  
  
  METHODS
  The Surveillance, Epidemiology, and End Results (SEER) database identified patients who underwent total thyroidectomy and lymph nodes excision for MTC between 1988 and 2004. The Kaplan-Meier method was used for univariate comparisons of OS. Multivariate Cox proportional hazards models controlled for gender, age, lymph node status, tumor size, extent of disease, and EBRT.
  
  
  RESULTS
  After 12 years, EBRT did not significantly improve OS (log rank, P < 0.14). In node-positive patients, univariate analysis demonstrated an OS benefit with EBRT (log rank, P < 0.05). In a multivariate model of node-positive patients, only increasing age (P < 0.001) and tumor size (P < 0.001) significantly influenced OS.
  
  
  CONCLUSIONS
  The OS benefit attributed to EBRT in node-positive patients by univariate analysis could not be duplicated when controlling for known prognostic factors.
authors.affiliation: Division of Surgical Oncology, Department of Surgery, UC Davis Cancer Center, University of California at Davis, Sacramento, California 95817, USA. steve.martinez@ucdmc.ucdavis.edu
authors.forename: Steve R
authors.initials: SR
authors.lastname: Martinez
authors.forename: Shannon H
authors.initials: SH
authors.lastname: Beal
authors.forename: Allen
authors.initials: A
authors.lastname: Chen
authors.forename: Steven L
authors.initials: SL
authors.lastname: Chen
authors.forename: Philip D
authors.initials: PD
authors.lastname: Schneider
mesh_terms: D000367:Age Factors; D018276:Carcinoma, Medullary / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D018714:Radiotherapy, Adjuvant; D018426:SEER Program; D013964:Thyroid Neoplasms / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy