Evaluation of a clinically applicable post-surgical classification system for primary retroperitoneal soft-tissue sarcoma

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.