title: External validation of a multi-institutional retroperitoneal sarcoma nomogram.
abstract: BACKGROUND
  A multi-institutional nomogram for predicting disease-free survival (DFS) and overall survival (OS) in patients with primary retroperitoneal sarcoma (RPS) incorporating relevant prognostic factors not included in the American Joint Committee on Cancer staging system for soft tissue sarcoma has been reported. The authors validated this nomogram with an independent, transatlantic cohort.
  
  
  METHODS
  Data from patients with RPS who were undergoing definitive resection at 1 of 6 sarcoma centers in Europe and North America ("validation set") were used to validate a RPS nomogram developed from 3 other centers ("development set"). The nomogram incorporated 6 variables: age, tumor size, grade, histologic subtype, multifocality, and quality of surgery. Nomogram-predicted probabilities were stratified into 6 subgroups and compared with observed outcomes. Discriminative ability was quantified by Harrell C statistics.
  
  
  RESULTS
  The validation and development sets included 631 and 523 patients, respectively, all of whom underwent surgical resection at the institutions represented. The 7-year DFS and OS rates for the validation set were 38% (95% confidence interval, 34%-43%) and 58% (95% confidence interval, 53%-63%), respectively. All 6 nomogram variables were found to be independently prognostic. The corrected Harrell C statistics concordance index values for the validation set were 0.69 for DFS and 0.73 for OS, which were similar to those for the development set, suggesting good calibration of the nomogram in the validation cohort.
  
  
  CONCLUSIONS
  The RPS nomogram was externally validated using a larger, independent cohort. The nomogram can be generalized to patients undergoing surgery for RPS by specialized sarcoma surgeons at sarcoma centers. The nomogram provides a more individualized and disease-relevant estimation of OS compared with the American Joint Committee on Cancer classification. Cancer 2016;122:1417-1424. © 2016 American Cancer Society.
authors.affiliation: Division of Surgical Oncology, Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.|Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
authors.forename: Chandrajit P
authors.initials: CP
authors.lastname: Raut
authors.affiliation: Department of Medical Statistics, Biometry and Bioinformatics, IRCCS Foundation National Cancer Institute, Milan, Italy.
authors.forename: Rosalba
authors.initials: R
authors.lastname: Miceli
authors.affiliation: Department of Surgery, Royal Marsden Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Dirk C
authors.initials: DC
authors.lastname: Strauss
authors.affiliation: Department of Surgical Oncology, Mount Sinai Hospital and Princess Margaret Cancer Centre, Toronto, Ontario, Canada.|Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Swallow
authors.affiliation: Division of Surgical Oncology and Thoracic Surgery, Mannheim University Hospital, Mannheim, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Hohenberger
authors.affiliation: Department of Surgical Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Frits
authors.initials: F
authors.lastname: van Coevorden
authors.affiliation: Department of Soft Tissue/Bone Sarcoma and Melanoma, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Rutkowski
authors.affiliation: Department of Surgery, IRCCS Foundation National Cancer Institute, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Fiore
authors.affiliation: Department of Surgery, IRCCS Foundation National Cancer Institute, Milan, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Callegaro
authors.affiliation: Department of Cancer Medicine, IRCCS Foundation National Cancer Institute, Milan, Italy.
authors.forename: Paolo G
authors.initials: PG
authors.lastname: Casali
authors.affiliation: Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Rick L
authors.initials: RL
authors.lastname: Haas
authors.affiliation: Department of Surgery, Royal Marsden Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hayes
authors.affiliation: Department of Surgery, Gustave Roussy Institute, Villejuif, France.
authors.forename: Charles
authors.initials: C
authors.lastname: Honore
authors.affiliation: Department of Surgical Oncology, Mount Sinai Hospital and Princess Margaret Cancer Centre, Toronto, Ontario, Canada.|Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Cannell
authors.affiliation: Division of Surgical Oncology and Thoracic Surgery, Mannheim University Hospital, Mannheim, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Jakob
authors.affiliation: Department of Soft Tissue/Bone Sarcoma and Melanoma, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Warsaw, Poland.
authors.forename: Milena
authors.initials: M
authors.lastname: Szacht
authors.affiliation: Division of Surgical Oncology, Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.|Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
authors.forename: Mark
authors.initials: M
authors.lastname: Fairweather
authors.affiliation: Division of Surgical Oncology, Department of Surgery, Ohio State University Medical Center, Columbus, Ohio.
authors.forename: Raphael E
authors.initials: RE
authors.lastname: Pollock
authors.affiliation: Department of Surgery, Curie Institute, Paris, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bonvalot
authors.affiliation: Department of Surgery, IRCCS Foundation National Cancer Institute, Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gronchi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001900:Boston; D016001:Confidence Intervals; D018572:Disease-Free Survival; D005260:Female; D005858:Germany; D006801:Humans; D008131:London; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009364:Neoplasm Recurrence, Local; D009426:Netherlands; D049451:Nomograms; D009864:Ontario; D011044:Poland; D012186:Retroperitoneal Neoplasms / Q000401:mortality* / Q000473:pathology / Q000601:surgery; D018426:SEER Program; D012509:Sarcoma / Q000401:mortality* / Q000473:pathology / Q000601:surgery; D047368:Tumor Burden
keywords: grade; histology; multifocality; nomogram; retroperitoneal sarcoma; staging; surgery