Long-Term Survival (Over 10 Years) Of Inoperable/Metastatic Gists: A Retrospective Series Of 141 Patients (Pts) Of The French Sarcoma Group (Fsg)

11041 Background: A subset of metastatic GIST exhibit very long-term survival after imatinib (IM) introduction. The aim of this study was to analyse the clinico-biological characteristics of GIST pts alive > 10 years (yrs) after diagnosis (dx) of metastases (mets) and identify possible factors associated with long-term survival. Methods: Pts were identified from 2 sarcoma databases; NetSarc and ConticaGIST. Clinical data prospectively registered in the databases were supplemented with retrospective review of medical records. Results: We identified 141 pts (75 men, 66 women) with median age 54 (17-84) yrs and median ECOG 0 (0-2). Primary tumors (T) were all CD117+, and mainly gastric or intestinal (64 & 45 pts), with median size 10 (2-40) cm, CD34+ (82 pts), mitoses/50 HPF ≤ 5 (n = 36), or > 5 (n = 81). Genotype was documented in 82 (58%) pts with 73 (89%) KIT mutations (in exons 11,9 and 12 of 69, 3, and 1 pts respectively) and 9 WT KIT. 129 (91%) T were resected, 124 upfront, 5 post IM, with R0/R1/R2 resections in 61, 11, and 10 pts. Mets were mainly hepatic or peritoneal (78 & 51 respectively). 1st line TKI was given to 139 pts: 130 received IM; 88 (63%) within a clinical trial (CT), 41 (29%) had mets resection. Second, 3d and 4th line TKI were given to 81, 51 and 37 pts respectively, comprising 27, 7 and 10 from CT. Median number of TKIs was 2 (0-7), but 60 (44%) pts received only 1st line with no GIST progression within or after 10 yrs. 2 pts never received TKI but had mets resection. After median FU of 14.3 yrs (10-34.5), 104 remain alive, 37 died. Mean and Median OS from initial dx are 24 yrs (CI95% 21.6-27) and 20,8 yrs. Median PFS on TKIs are 127, 29, 21 and 22 mos on 1st, 2d, 3d and 4th line of TKI. In univariate analysis no factor is significantly associated with OS, but T size (≤ 10 vs > 10 cm) and oligometastatic disease (≤5 vs > 5 mets) are borderline significant (p = 0.056 and 0.07), and good PS (ECOG ≤ 1) at 2dline TKI initiation is associated with better PFS (p = 0.03). Conclusions: This large series of long-term ( > 10 yrs) survivors of metastatic GIST shows a high proportion of mets resection and a longer duration of PFS for TKI at any line. In this selected population, no prognostic factor is associated with long OS.