title: Evaluation of a clinically applicable post-surgical classification system for primary retroperitoneal soft-tissue sarcoma.
abstract: BACKGROUND
  The present AJCC/TNM staging system is of limited value for prediction of prognosis for patients with retroperitoneal sarcoma. The objective of the present study was to develop a postsurgical classification system that would enable comparison of outcomes for patients with primary retroperitoneal soft-tissue sarcoma.
  
  
  METHODS
  Four classes were defined: I, low-grade/complete resection/no metastasis; II, high-grade/complete resection/no metastasis; III, any-grade/incomplete resection/no metastasis; and IV, any-grade/any resection/distant metastasis. The prognostic value of this classification system was analyzed in a population-based multicenter group(MCG) of patients with primary retroperitoneal soft-tissue sarcoma (n = 124) and in a cohort of patients treated in a single tertiary referral center (SCG; n = 107).
  
  
  RESULTS
  Overall 5-year survival rates were 55% in the SCG and 43% in the MCG (P = 0.02). Class III (incomplete resection) was more frequent in the MCG than in the SCG (33% vs. 16%; P = 0.02). In the SCG, stage-specific 5-year survival rates were 89%, 40%, 26%, and 17% for classes I, II, III, and IV, respectively (P < 0.001), in comparison with 68%, 46%, 24%, and 0% in the MCG (P < 0.001). In a comparison of class-specific survival between the groups, only class I patients in the SCG had significantly better survival than class I patients in the MCG (P = 0.048).
  
  
  CONCLUSIONS
  Classification based on grade, completeness of resection, and distant metastasis offers a reproducible prognostic tool that can be used to evaluate treatment strategies for primary retroperitoneal soft-tissue sarcoma. The probability of complete resection was significantly higher in the SCG than in the MCG. In patients with low-grade, completely resected sarcoma, there is a significant survival benefit with treatment in a high-volume tertiary center of excellence.
authors.affiliation: Dutch Soft Tissue Sarcoma Group, Vereniging van Integrale Kanker Centra, Utrecht, The Netherlands.
authors.forename: Thijs
authors.initials: T
authors.lastname: van Dalen
authors.forename: Adriaan
authors.initials: A
authors.lastname: Hennipman
authors.forename: Frits
authors.initials: F
authors.lastname: Van Coevorden
authors.forename: Harald J
authors.initials: HJ
authors.lastname: Hoekstra
authors.forename: Bert N
authors.initials: BN
authors.lastname: van Geel
authors.forename: Piet
authors.initials: P
authors.lastname: Slootweg
authors.forename: Cherry F Albus
authors.initials: CF
authors.lastname: Lutter
authors.forename: Murray F
authors.initials: MF
authors.lastname: Brennan
authors.forename: Samuel
authors.initials: S
authors.lastname: Singer
mesh_terms: D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging / Q000379:methods*; D011379:Prognosis; D012186:Retroperitoneal Neoplasms / Q000145:classification / Q000473:pathology* / Q000601:surgery*; D012509:Sarcoma / Q000145:classification / Q000473:pathology* / Q000601:surgery*; D012680:Sensitivity and Specificity; D012983:Soft Tissue Neoplasms / Q000145:classification / Q000473:pathology* / Q000601:surgery*; D016019:Survival Analysis; D016896:Treatment Outcome