title: Development and internal validation of a prognostic model to predict recurrence free survival in patients with adult granulosa cell tumors of the ovary.
abstract: OBJECTIVE
  Models to predict the probability of recurrence free survival exist for various types of malignancies, but a model for recurrence free survival in individuals with an adult granulosa cell tumor (GCT) of the ovary is lacking. We aimed to develop and internally validate such a prognostic model.
  
  
  METHODS
  We performed a multicenter retrospective cohort study of patients with a GCT. Demographic, clinical and pathological information were considered as potential predictors. Univariable and multivariable analyses were performed using a Cox proportional hazards model. Using backward stepwise selection we identified the combination of predictors that best predicted recurrence free survival. Discrimination (c-statistic) and calibration were used to assess model performance. The model was internally validated using bootstrapping techniques to correct for overfitting. To increase clinical applicability of the model we developed a nomogram to allow individual prediction of recurrence free survival.
  
  
  RESULTS
  We identified 127 patients with a GCT (median follow-up time was 131 months (IQR 70-215)). Recurrence of GCT occurred in 81 out of 127 patients (64%). The following four variables jointly best predicted recurrence free survival; clinical stage, Body Mass Index (BMI), tumor diameter and mitotic index. The model had a c-statistic of 0.73 (95% CI 0.66-0.80) and showed accurate calibration.
  
  
  CONCLUSIONS
  Recurrence free survival in patients with an adult GCT of the ovary can be accurately predicted by a combination of BMI, clinical stage, tumor diameter and mitotic index. The introduced nomogram could facilitate in counseling patients and may help to guide patients and caregivers in joint decisions on post-treatment surveillance.
authors.affiliation: Department of Obstetrics and Gynecology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: h.s.vanmeurs@amc.nl.
authors.forename: Hannah S
authors.initials: HS
authors.lastname: van Meurs
authors.affiliation: Department of Obstetrics and Gynecology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands. Electronic address: e.schuit@umcutrecht.nl.
authors.forename: Ewoud
authors.initials: E
authors.lastname: Schuit
authors.affiliation: Department of Pathology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: h.m.horlings@amc.nl.
authors.forename: Hugo M
authors.initials: HM
authors.lastname: Horlings
authors.affiliation: Department of Obstetrics and Gynecology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: j.vandervelden@amc.nl.
authors.forename: Jacobus
authors.initials: J
authors.lastname: van der Velden
authors.affiliation: Department of Gynecology, Center for Gynecologic Oncology Amsterdam, Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. Electronic address: w.v.driel@nki.nl.
authors.forename: Willemien J
authors.initials: WJ
authors.lastname: van Driel
authors.affiliation: The Robinson Institute, School of Pediatrics and Reproductive Health, University of Adelaide, Level 3 Medical School South Building, Frome Road, SA 5005 Adelaide, Australia. Electronic address: b.w.mol@amc.nl.
authors.forename: Ben Willem J
authors.initials: BW
authors.lastname: Mol
authors.affiliation: Department of Obstetrics and Gynecology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: g.g.kenter@amc.nl.
authors.forename: Gemma G
authors.initials: GG
authors.lastname: Kenter
authors.affiliation: Department of Obstetrics and Gynecology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: m.r.buist@amc.nl.
authors.forename: Marrije R
authors.initials: MR
authors.lastname: Buist
mesh_terms: D000328:Adult; D015331:Cohort Studies; D018572:Disease-Free Survival; D005260:Female; D006106:Granulosa Cell Tumor / Q000453:epidemiology / Q000628:therapy; D006801:Humans; D008875:Middle Aged; D015233:Models, Statistical; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology; D049451:Nomograms; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000628:therapy; D011379:Prognosis; D012189:Retrospective Studies
keywords: Granulosa cell tumor; Nomogram; Ovarian cancer; Prognosis; Recurrence