Tumor regression grade after neoadjuvant chemotherapy in patients with locally advanced gastric cancer treated with modern chemotherapy (FLOT): Experience in patients in Guatemala.

Abstract

287 Background: Perioperative chemotherapy is the standard of care for locally advanced gastric cancers in Western populations. At this moment perioperative chemotherapy with FLOT (Fluorouracil, leucovorin, oxaliplatin and docetaxel) regimen is recommended in patients who are medically fit with benefit in progression-free survival (PFS) and overall survival (OS). However, the impact of response to this treatment is not well established. The objective of this study is to find the pathological response to FLOT chemotherapy measured by the degree of tumor regression (TRG), the benefit on disease-free survival (DFS) and OS, in patients with gastric cancer locally advanced treated with FLOT chemotherapy. Methods: Patients from the Instituto Guatemalteco de Seguridad Social (IGSS) from Guatemala City, who underwent radical gastrectomy for non-metastatic invasive gastric adenocarcinoma after perioperative chemotherapy (T1-4/N0/N+cM0) from 2019 to 2023 were included. Demographic data, clinical staging, histologic phenotype, surgical factors, tumor regression grade after gastrectomy and survival outcomes were included. The association between ORR and OS were evaluated. OS and DFS were estimated using the Kaplan Meier method with adjustment for covariates using Cox regression. Results: Thirty-eight patients with locally advanced cancer gastric were identified. The median age was 58 years (29-79), most of the patients were men (23, 61%), 35 (92%) patients have primary gastric tumor, 26 (68%) has cT3/T4 tumors and 22 (58%) has intestinal gastric cancer, all patients underwent to surgery. Two patients (6%) had TRG of 1 (complete and almost complete), 8 patients (21%) had an TGR of 2, and 28 patients (74%) had an TGR of 3; 13 patients (38%) developed recurrence, median DFS was 5.2 months (95% CI: 1.0–28). The median OS was 15.3 months (95% CI: 3.0-45). Lack of tumor regression (TRG 3) was significantly associated with lower survival HR 1.42 (1.05-2.24) p= 0.008. Clinical T4 tumors and diffuse histology were associated with poor prognostic (cT4 HR 3.04, p = 0.038, diffuse histology HR 2.08 (p = 0.001) (Table). Conclusions: Since cT4 tumors are an independent risk factor associated with poor prognostic HR 3.04, p = 0.038, it is important to make an adequate clinical staging before deciding to use three-drug treatment regimens of chemotherapy. Other factors in addition to clinical ones should be investigated, such as molecular factors that may be related to this poor response and survival in patients with cT4. This study of molecular factors is currently underway at our institution. [Table: see text]