REGOSTA: A randomized, placebo-controlled, double-blinded, multicenter study evaluating the efficacy and safety of regorafenib (REGO) as maintenance therapy after first-line treatment in patients (pts) with osteosarcoma (OS) and non-osteosarcomas (non-OS) of bone (non-Ewing, non-chondrosarcomas and non-chordomas)

TPS11576

Background: Pts with OS and non-OS of bone are treated with a multimodal sequence therapy of neoadjuvant chemotherapy (CT), surgery and adjuvant CT, followed by a close surveillance until recurrence. At recurrence, the prognosis remains poor with objective response rates of 3-29%, and a median Progression-Free Survival (PFS) of less than 4 months in OS. There is a clinical need to reduce the risk of recurrence after the initial treatment sequence. The REGOBONE study reported a significant clinical benefit of regorafenib compared to placebo in patients with relapsed OS (median PFS: 16.4 versus 4.1 weeks). Methods: This multicenter trial is ongoing to study the efficacy and safety of maintenance REGO in pts > = 16 years, with complete remission after initial treatment sequence of their bone sarcoma. 168 pts will be randomly allocated in a 1:1 ratio to receive either oral REGO or its matching placebo (control arm) at a daily dose of 120mg, continuously and for a maximum of 12 months. Randomization will be stratified according to the following risk factors: metastases (mets) at diagnosis and/or poor response to neoadjuvant CT versus no mets at diagnosis and good response to neoadjuvant CT. The primary objective is to compare the efficacy (Relapse-Free Survival) between the 2 arms. The expected 3-year RFS rates are 55% in the control arm and 74.6% in the REGO arm (HR = 0.5). 66 events will provide 80% power to show significant improvement in RFS, using a 2-sided log-rank test at a 5% level. Secondary endpoints include Time to Treatment Failure, Overall Survival, Quality of Life, safety profile, and compliance to treatment. Radiological endpoints will be evaluated using the RECIST 1.1. Translational objectives will be to identify predictive biomarkers for efficacy of REGO as maintenance therapy using liquid biopsies. As of Feb 1st, 2021, 3 patients have been randomized. 15 sites of the French Sarcoma Group will participate. Clinical trial information: NCT04055220.

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.

Clinical experience with sunitinib (SU) in patients over age 65 with metastatic gastrointestinal stromal tumors (GIST): A retrospective study from the French Sarcoma Group (FSG)

10546

Background: Elderly GIST patients (pts) represent a consistent portion of all GIST pts, but are under-represented in clinical trials. Data on benefits, tolerance of SU in elderly GIST pts and their specific outcome are very limited. Methods: Charts of elderly pts (≥ 65 yrs)treated with SU in routine clinical practice from 11 Centres of the FSG were reviewed to evaluate the efficacy and safety of SU. Results: 71 elderly GIST pts were reviewed, with a median age of 74, [distributed as 65-74, n=36; 75-84, n=30; ≥ 85, n=5], 41 (57%) men, with median ECOG-PS= 1 (0-2), and median active comorbities of 1 (0-4). SU was administered after progression on first-line Imatinib (400 mg/d for 21 pts, 400 then 800 mg/d for 45 pts) or masitinib (5 pts). SU was started at 50 mg/d 4-wks-on/2 wks-off in 37 pts (52%), at 37.5 mg daily in 32 pts (45%), and at 25 mg daily in 2 pts. All but 2 pts experienced at least one adverse event (AE). Drug related AE were mainly of grade 1 or 2 (298/388, 76%), and medically manageable. Most frequent AE were fatigue (20%), diarrhea (11%), mucositis (7%), abdominal pain (7%), hand-foot syndrome (6%), neutropenia (6%), and hypertension (5%). Permanent dose reduction was reported in 33 pts (46%). In 17 pts (24%) SU was permanently stopped due to grade 3 or 4 AE. ; this occurred within 3 months after starting SU in 10 pts. At a median 36 months follow-up, 53 pts progressed, and 28 pts were alive. The median PFS and OS were 10.2 (0.2-54) and 21 (0.5-77) months, respectively. Univariate analysis showed that age (≤ 80), PS (<1), WBC (≤ 4 Giga/l), Hb and Albumin have a positive impact on OS (all p < 0.04) and PFS (all p < 0.05). In multivariate analysis, Albumin and Hb had an impact on OS and PFS, PS had an impact only on OS, and WBC only on PFS. A correlation was found between comorbidities and Grade 3/4 toxicities, but no correlation between any toxicities and outcome. Conclusions: Compared to data from clinical trials, SU yields similar rates of GIST control and OS in elderly pts despite frequent dose reductions or interruptions. Since comorbidities may increase the risks of AEs, careful follow-up to assess tolerance is particularly indicated in elderly GIST pts.

Association of circulating VEGF-A levels with outcome in patients with vascular sarcomas receiving sorafenib (Sor): Exploratory analysis from AngioNext study

10525

Background: We have carried out a stratified phase II study of Sor in pts with advanced angiosarcoma (AA, n=32), malignant solitary tumour (SFT, n=4) & epithelioid hemangioendothelioma (EE, n=13). We report here the correlative analysis of predictive value of circulating pro/anti-angiogenetic biomarkers. Methods: Using ELISA method (R&D SYSTEMS) Circulating biomarkers (VEGF-A [pg/mL], Thrombospondin-1 (TSP1) [µg/mL], Stem Cell Factor (SCF) [pg/mL], Placental growth factor (PlGF) [pg/mL], VEGF-C [pg/mL] & E-selectin [ng/mL]) have been measured before Sor treatment & after 7 days. We analyze the correlation with histological subtypes, presence of metastases, best response and occurrence of hemorrhage and Gr3-4 arterial hypertension. Results: VEGF-A (mean value 475 vs 541 pg/mL, p=0.002), TSP1 (16 vs 24 µg/mL, p=0.0002), PlGF (20.9 vs 40.7 pg/mL, p=0.0001) significantly increased during the treatment. Sor treatment did not affect the levels of SCF, VEGF-C & E-selectin. The distributions of all biomarkers were similar across the histological subtypes, whatever the presence of metastasis, the occurrence of hemorrhage or arterial hypertension. 2 biomarkers were associated with better outcome:VEGF-A & PlGF. Best objective response and non-progression at 180 days were associated with low level of VEGF-A at baseline (p=0.04 and p= 0,03 respectively). There was a correlation between circulating level of VEGF-A & time to progression (TTP) (r=-0.47, p=0.001). Best objective response and non-progression at 180 days were not associated with baseline level of PlIGF (p=0.34 and 0.07), but there was a correlation between circulating level of PlIGF at baseline and TTP (-0.31, p=0.02). Conclusions: In pts with vascular sarcomas receiving Sor, we have observed a significant decrease in circulating level of VEGF-A. Low level of VEGF-A at baseline (<500 pg/mL) was significantly associated with better outcome, especially best objective response rate, non-progression at 180 days and time to progression. Clinical trial information: 2007-004651-10.

Primary localized gastrointestinal stromal tumors (GIST) of the duodenum: Final results of a French Sarcoma Group (FSG) retrospective review of 110 patients (pts)

10078

Background: Duodenal GISTs represent 3-5% of all GISTs with limited understanding of patient outcomes from small series. We conducted a retrospective analysis of primary localized duodenal GISTs over the past 18 years. Methods: Pts were identified in two ways: a group of 101 pts reported via survey from 20 FSG centers, and a group of 9 pts enrolled in the BFR14 trial. Results: Pts were:55 females, 55 males, with a median age of 57 years (30-84), and median ECOG 0 (0-3). Abdominal pain, anemia, and GI bleeding were the most common symptoms. Tumors (T) originated mainly in D2 (41%), or D3 (27%), with a median size of 5 cm (1.5-30). All pts except four had resection of the primary T. Surgical procedures were: local resection (LR) [segmental duodenectomy (n=31), wedge local resection (n=31), local excision (n=6)], and duodenopancreatectomy (DP, n=20). Resections were R0 in 84 pts (79%), R1 in 6 pts (6%). T characteristics included: KIT+ (n=100), CD34 + (n= 54), mitoses/50 HPF ≤ 5 (n= 70), or > 5 (n=24), Miettinen low-risk (n=37), and high-risk (n=19), necrosis (n=29), spindle cell (n=84). Genotype was evaluated in 36 cases: KIT exon 11 mutant (n=30), no mutation (n=4), and KIT exon 9 mutant (n=2). 12 pts received neoadjuvant imatinib (IM) therapy resulting in 6 PR, 3 SD, 1 PD. 17 pts received adjuvant IM therapy. With a median FU of 32 months (1-250), 95 pts (86%) are alive. Twenty-eight (26%) pts relapsed: 6 LR, and 26 metastases. The 4-year OS and EFS rates were 89.5% and 68.2 %. The 6-year OS and EFS rates were 89.5% and 36.5%. Univariate analysis showed that: age and ECOG PS have an impact on OS (p= 0.008, p <0.001), necrosis, spindle-cell type, T size, mitoses/50 HPF, and Miettinen risk were predictive of relapse (p< 0.001). In multivariate analysis tumor size and mitoses/ 50 HPF only were predictive of relapse (p< 0.001). Conclusions: Pts with resected duodenal GIST have a reasonably favourable prognosis. LR rather than DP should be pursued if possible to preserve optimal pancreas function. Neoadjuvant IM may potentially allow a proportion of patients requiring DP to undergo LR. Adjuvant IM should be systematically discussed with a patient based on the individual-risk of recurrence.