title: Determinants of outcome of solitary fibrous tumors of the pleura: an observational cohort study.
abstract: BACKGROUND
  Solitary fibrous tumors of the pleura (SFTP) are rare and their long-term outcome is difficult to predict, as there are insufficient data which allow accurate characterization of the malignant variant. Thus the aim of this study was to describe the outcome and possible determinants of malignant behavior of SFTPs.
  
  
  METHODS
  Data were collected retrospectively from medical records of patients treated at the University Hospital Zurich from 1992 to 2012. Kaplan-Meier and Cox regression analysis were performed to define disease-free survival time (defined as survival without tumor-recurrence or tumor-related death) using the classical histo-morphological criteria (tumor size, localization, pedunculation, tumor necrosis or hemorrhage, mitotic activity and nuclear pleomorphism) and immunohistochemical parameters.
  
  
  RESULTS
  42 patients (20 males) with SFTP (median (IQR) age 62 (56-71) years) could be identified. SFTP were associated with symptoms in 50% of all cases. Complete resection was achieved by video-assisted thoracic surgery or thoracotomy in 20 and 22 patients, respectively. Three SFTP-related deaths (7.1%) and four tumor recurrences (9.5%) were observed. Mean disease-free survival time was 136.2 (± 13.1) months, and 2-, 5- and 10-year disease-free survival was 91%, 84%, and 67%, respectively. Mean disease-free survival inversely correlated with the mean tumor diameter, number of mitotic figures and proliferation rate (Ki-67 expression). Other criteria (tumor necrosis, atypical localization, sessile tumor, and pleomorphism) were not statistically significant prognostic parameters.
  
  
  CONCLUSIONS
  Patients with large SFTP with a high mitotic index and high proliferation rate should be followed-up closely and over a prolonged time period in order to recognize recurrence of the SFTP early and at a treatable stage. Future research on this topic should focus on the prognostic role of immunohistochemistry including Ki-67 expression and molecular parameters.
authors.affiliation: Division of Pulmonology, University Hospital Zurich, Rämistrasse 100, 8091 Zurich, Switzerland. daniel.franzen@usz.ch.
authors.forename: Daniel
authors.initials: D
authors.lastname: Franzen
authors.forename: Matthias
authors.initials: M
authors.lastname: Diebold
authors.forename: Alex
authors.initials: A
authors.lastname: Soltermann
authors.forename: Didier
authors.initials: D
authors.lastname: Schneiter
authors.forename: Peter
authors.initials: P
authors.lastname: Kestenholz
authors.forename: Rolf
authors.initials: R
authors.lastname: Stahel
authors.forename: Walter
authors.initials: W
authors.lastname: Weder
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
mesh_terms: D000368:Aged; D049109:Cell Proliferation; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D019394:Ki-67 Antigen / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D008940:Mitotic Index; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D054363:Solitary Fibrous Tumor, Pleural / Q000737:chemistry* / Q000473:pathology* / Q000601:surgery; D020775:Thoracic Surgery, Video-Assisted; D047368:Tumor Burden
chemical_list: D019394:Ki-67 Antigen