P-68 Response to neoadjuvant chemotherapy in gastric adenocarcinoma and gastroesophageal junction adenocarcinoma with FLOT-regimen in our setting

Abstract

As a result of the FLOT4 trial, the FLOT-regimen has been proven effective in the perioperative treatment of locally advanced and potentially resectable gastric adenocarcinoma and gastroesophageal junction (GEJ) adenocarcinoma. Subsequent analyses revealed higher R0-resection and pathologic complete response (pCR) rates in intestinal-type tumors and GEJ location. This study was a retrospective descriptive analysis of data from patients who have been diagnosed with gastric and GEJ adenocarcinomas in a locally advanced and potentially resectable stage. The patients included were treated between April 2017 and September 2020 at the Hospital Universitario Virgen del Rocío, receiving perioperative chemotherapy with FLOT (docetaxel 50 mg/m2, oxaliplatin 85 mg/m2, 5-fluorouracil 2600 mg/m2, and leucovorin 200 mg/m2). The analysis aimed to evaluate the pathological response of the tumor after neoadjuvant chemotherapy, based on location (gastric and GEJ) and tumor histological subtype (diffuse/mixed type and intestinal type). Among the 34 patients included (73% males), 11 (32.4%) had an intestinal-type tumor, 21 (61.7%) had diffuse/mixed, and 2 (5.9%) had indeterminate type. The median age was 59.5 years, higher in the intestinal group (62 years) than in the diffuse/mixed group (53 years). The location of the tumor was gastric in 25 (73.5%) patients and CEJ in the remaining 9 (26.5%). Only 2 (5.9%) patients were HER2-positive, one with intestinal-type and the other with diffuse/mixed type; and 13 (38.2%) had signet ring cell, all of them with a diffuse/mixed tumor, except one with unknown histology. The complete surgical resection after the neoadjuvant (described as R0-resection) was achieved in 90.9% (n=10) of the intestinal group and in 71.4% (n=15) of the diffuse/mixed, while the R1-resections was achieved in only 14.3% (n=3) of the intestinal group. During the surgery, 6 (17.6%) patients were unresectable because of local progression and invasion of unresectable structures, or because of distant metastases appearance. Among this group, 3 had a diffuse/mixed tumor, 1 had intestinal-type, and 2 had an indeterminate type. The pathologic complete response in surgical specimens, defined as T0N0, was achieved in 5 (14.7%) patients, one of them had a diffuse/mixed tumor and the rest had intestinal type. Regarding the tumor location, 4 had a gastric tumor and 1 had GEJ. After the analysis of the post-neoadjuvant staging (following the 8th edition of the AJCC-TNM classification), the following results were obtained: 18 patients had a lower stage (10 intestinal and 8 diffuse/mixed), 10 had a higher stage (7 diffuse/mixed, 1 intestinal and 2 unknown), and the stage of the other 6 did not change (all of them diffuse/mixed). The results of this study are in accordance with those obtained in the published series, as the pathological response to neoadjuvant with FLOT in tumors with intestinal histology has been better than the response in diffuse/mixed (90.9% R0-resection and 36.3% pRC; 71.4% R0-resection and 4.7% pRC). However, the pRC rates and complete resection rates were lower for GEJ than gastric tumors (44.5% R0-resection and 11.1% pRC; 84% R0-resection and 16% pRC).