title: Growth dynamics of plexiform neurofibromas: a retrospective cohort study of 201 patients with neurofibromatosis 1.
abstract: BACKGROUND
  To examine the natural growth dynamics of internal plexiform neurofibromas (PNs) in patients with neurofibromatosis 1 (NF1).
  
  
  METHODS
  Two hundred and one NF1 patients underwent whole body MRI (WBMRI). Tumour burden was estimated volumetrically. Non-parametric Spearman's rho correlation coefficients were used to analyse the relationship of growth rate to tumour volume and age. Chi-squared and Mann-Whitney U tests were used for analysing the association of tumour occurrence with sex or age. Chi-squared tests were used to analyse the association of tumour growth with age group.
  
  
  RESULTS
  Seventy-one of 171 patients with serial WBMRI exams had internal PNs (median follow up 2.2 years [1.1 to 4.9 years]). Median whole body tumour volume was 86.4 mL [5.2 to 5878.5 mL]) with a median growth rate of 3.7%/year (-13.4 to 111%/year) that correlated with larger whole body tumour volume (P<0.001) and lower age (P=0.004). No new PNs developed in 273.0 patient-years among patients without tumours. Rate of new tumour development among patients with PNs was 0.6%/year (95% confidence interval 0.02 to 3.4%). Twenty-seven (13.5%) tumours increased significantly and were more frequent among children (P<0.001). Growth rate of tumours was inversely correlated with age (Spearman's rho=-0.330, P<0.001). Seventy-one (35.5%) tumours had smaller volumes on follow up (median -3.4%/year [-0.07% to -35.9%/year]).
  
  
  CONCLUSIONS
  Children with NF1 and internal PNs are at risk for tumour growth. Most PNs grow slowly or not at all, and some decrease in size. New tumours are infrequent in NF1 patients with PNs and unlikely in patients without PNs.
authors.affiliation: Department of Neurology, University Hospital Hamburg-Eppendorf, Hamburg, Germany. rosi.nguyen@gmail.com
authors.forename: Rosa
authors.initials: R
authors.lastname: Nguyen
authors.forename: Eva
authors.initials: E
authors.lastname: Dombi
authors.forename: Brigitte C
authors.initials: BC
authors.lastname: Widemann
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Solomon
authors.forename: Carsten
authors.initials: C
authors.lastname: Fuensterer
authors.forename: Lan
authors.initials: L
authors.lastname: Kluwe
authors.forename: Jan M
authors.initials: JM
authors.lastname: Friedman
authors.forename: Victor-Felix
authors.initials: VF
authors.lastname: Mautner
mesh_terms: D016009:Chi-Square Distribution; D006801:Humans; D008279:Magnetic Resonance Imaging; D018318:Neurofibroma, Plexiform / Q000473:pathology*; D009456:Neurofibromatosis 1 / Q000473:pathology*; D012189:Retrospective Studies