1584P Conversion effect of PD-1 antibody camrelizumab (Cam) combined with modified FLOT (mFLOT) regimen in patients(pts) with initially unresectable locally advanced or limited metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma

The AIO-FLOT3 Trial suggested that conversion therapy might improve outcome in pts with metastatic gastric cancer (GC). We conducted this prospective, single-arm, phase II trial to improve conversion efficacy of ICIs combined with mFLOT regimen (fluorouracil, oxaliplatin, and nab-PTX) in pts with initially unresectable locally advanced or limited metastatic GC or GEJ adenocarcinoma. Eligible pts received Cam 200mg, oxaliplatin 85 mg/m2, nab-PTX 125 mg/m2 or with trastuzumab if Her2 positive, each was an IV followed by fluorouracil 2400 mg/m2 as a 48-h continuous iv on day 1, every 2 weeks. Pts were assessed for tumor response and surgical feasibility every 3 cycles. The primary endpoint was R0 conversion rate. 35 pts were enrolled up to 04/2023. 30 pts were evaluable. The median age was 50y. Male was 76.7%. The metastatic sites included liver 50.0% (15), retroperitoneal lymph nodes (LNs) 33.0% (10), axillary and supraclavicular LNs 6.7% (2), Krukenberg 3.3% (1), adrenal gland 3.3% (1), and locally advanced unresectable 10% (3). 7(23.3%) pts had two or more unresectable lesions. 4 pts were dMMR/MSI-H and 4 were Her2 positive. ORR was 86.7% and DCR was 96.7%. 25(83.3%) pts were assessed as resectable after conversion therapy. One pt refused surgery and 2 were cCR under observation. 22 pts (73.3%) received operation with R0 resection and no perioperative mortality. With 2 cCR included, R0 conversion rate was 80.0% (24/30). 5 pts (22.7%) achieved pCR and 12(54.5%) achieved MPR. Grade 3 AEs included 2 cases of rash, 1 case of adrenal insufficiency, 1 case each of ALT, AST elevation and febrile neutropenia. 1 pt was Grade 4 Neutrophil count decreased. (Table) Table: 1584PResponse and surgical conversion, n (%)N=30ORR26 (86.7）CR2 (6.7)PR24 (80.0)DCR29 (96.7)SD3 (10.0)PD1 (3.3)R0 conversion rate24 (80.0)Pathological responsepCR5/22 (22.7)MPR12/22 (54.5)cCR+pCR7 (23.3) Open table in a new tab Cam combined with mFLOT regimen safely induced a high conversion rate, with very high R0 resection, pCR and MPR. The findings warrant further prospective investigations.