Survival Impact Of Surgical Management In Reference Centers For Retroperitoneal Sarcoma: A Nationwide Study Of Fsg-Geto And Netsarc.

11568 Background: Retroperitoneal sarcoma (RPS) are complex to treat. We previously reported that management and surgery in a reference center are independent prognostic factors for relapse free survival (RFS) in sarcoma. Here, we investigated the impact of the surgery in a reference center on RFS and overall survival (OS) in the nationwide NETSARC study. Methods: NETSARC (netsarc.org) is a network of 26 reference sarcoma centers, funded by the French NCI. Since 2010, second pathological review are mandatory for sarcoma patients (pts) facilitating exhaustive collection. Pts characteristics and follow-up are collected in a database regularly monitored. From 2010 to 2016, RPS represented 10.0% (range 8.3-10.5%) of all sarcomas included in Netsarc. Results: 1286 RPS (M/F ratio: 1.09, median age 63, range 20-94) are reported in NETSARC from 01/2010 to 12/2016. WD/DDDLPS (63.7%), LMS (21,3%), UPS (6,3%) were the most frequent histotypes. 155 (12%) pts had metastasis (met) at diagnosis. 699 (54%) and 587 (46%) were presented to one of the 26 NETSARC multidisciplinary board before and after initiation of treatment. 477 (37%) and 809 (63%) were operated within vs outside a NETSARC reference center. The former group had larger tumor size, p < 0.0001, but no difference of age, grade, histotypes. More pts treated in NETSARC centers had documented imaging (92% vs 80%) and preoperative biopsy (81% vs 63%, p < 0.0001 both). Quality of final surgery was R2 or unknown, in 24% vs 69% in NETSARC vs non NETSARC centers (p < 0.0001). In univariate analysis on non met patients, surgery within a reference center was associated with a better OS (median not reached: 30-months OS 84% vs 63% respectively, logrank p < 0.001). Local RFS and RFS were significantly better for pts operated in reference centers (p < 0.0001). Surgery in reference center was an independent good prognostic factor for OS (HR: 0.23), LRFS (HR:0,56), RFS (HR:0,79) using Cox model (p < 0.001 all). Conclusions: In this nationwide unselected population of RPS over 7 years period, surgery in reference center is associated with a major reduction of the risk of relapse and death.