Outcome of 91 Clear Cell Sarcoma Tumor Patients: A Retrospective Study from the French Sarcoma Group (GSF-GETO).

11552 Background: Clear-Cell Sarcoma (CCS) is a rare soft tissue sarcoma poorly documented, with poor prognosis. Primary objective was to study the characteristics and outcomes of CCS patients (pts). Methods: Retrospective study from the nation-wide French sarcoma network (NetSarc) from 1991 to 2017. Inclusion criterion was CCS central pathological review. Endpoints were local recurrence-free survival (LRFS), metastatic-free survival (MFS), disease-free survival (DFS) and overall survival (OS). Results: 91 pts from 16 centers were included (molecular biology confirmed in 53% pts). Pts were aged 41 years (18-73), 57.1% men. The median tumor size was 4 cm (3-17). Patients were divided in 3 groups: localized (L) (61.5%), locally-advanced (LA) (15.4%), metastatic (M) (23.1%). Presurgical biopsy was performed in 50.7% of pts. All L and LA CCS pts underwent surgery, which was conservative in 70.6% pts. R0 resection was achieved in 71.9% of pts with 42.4% surgical revision to obtain clear margins. After a median follow-up of 6.5 years (95% CI: 4.5-9), 16 (22.9%), 37 (52.9%), 45 (64.3%), 29 (41.4%) events for LRFS, MFS, DFS and OS, were reported. Prognostic factors of the univariate analysis in L and LA pts are presented in Table 1. (Neo)Adjuvant radiotherapy and chemotherapy were performed in 54.4% and 30.9% pts, respectively, with no impact on OS or DFS. The 5-year OS rate for the 91 pts was 53.8% (95% CI: 41.70-64.22). For M pts, median OS was 12.7 months (95% CI: 10.4-21.5). Poor prognostic factors found in univariate analysis were male gender, delay between diagnosis and metastatic stage < 24 months, metastases other than pulmonary, and no surgery for metastatic disease. Conclusions: It's the largest study on CCS since the 1990s, with a large proportion of molecular biology confirmation. Stage, tumor necrosis, tumor size and localization are poor prognosis factors. Endpoint Variable Hazard Ratio (95% CI) p OS Stage Localized 1 0.0128 Locally Advanced 2.76 [1.2 ; 6.37] Tumor Size (mm) < 50 1 0.0171 ≥50 2.82 [1.16 ; 6.85] DFS Stage L 1 0.0253 LA 2.21 [1.08 ; 4.53] Tumor necrosis Yes 1 0.0473 No 2.30 [1.00 ; 5.36] Tumor Size (mm) < 50 1 0.0304 ≥50 2.18 [1.06 ; 4.49] Localization Members 1 0.0335 Other 2.08 [1.04 ; 4.13]