Irinotecan-based Triplet (FOLFOXIRI) as Perioperative Treatment in Resectable Gastric and Gastroesophageal Junction Adenocarcinoma.

Inclusion Criteria: * Histologically verified, resectable gastric or gastroesophageal (GE) (gastroesophageal) junction (Siewert type I-III) adenocarcinoma Confirmation of patient operability by surgeon * Primary tumor, regional nodes, metastasis (TNM), 8th edition): cT2-4a or cN+, cM0 * Age: 18 years or older * World Health Organization (WHO) performance status ≤ 1 * Exclusion of peritoneal carcinomatosis (if clinically suspected) via laparoscopy * Adequate laboratory findings: * hematological: hemoglobin \> 90 g/L (transfusion is allowed to attain this), absolute neutrophil count (ANC) ≥ 1,5 x 109/L, platelets ≥ 75 x 109/L * hepatic: bilirubin ≤ 1.5 x upper limit of normal (ULN), alanine aminotransferase (ALAT) ≤ 3 x ULN * renal: creatinine ≤ 1.5 x ULN (upper limit of normal) * Fertile men and women must use highly effective means of contraception (failure rate \<1%) such as: * combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal administration) * progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable administration) * intrauterine device * intrauterine hormone-releasing system * bilateral tubal occlusion * vasectomised partner * sexual abstinence * Signed written informed consent * The patient must be able to comply with the protocol Exclusion Criteria: * Neuroendocrine or adenosquamous carcinoma * Prior oncological treatment or surgical resection for the present disease * Presence of other concurrent malignancies or previous malignancies within 5 years except for adequately treated basal or squamous cell carcinoma of the skin or in-situ carcinoma of the cervix uteri * Clinically significant (i.e. active) cardiovascular disease e.g. myocardial infarction (≤ 6 months), unstable angina, New York Heart Association (NYHA) grade III-IV congestive heart failure * Active inflammatory bowel disease * Symptomatic peripheral neuropathy greater than grade 1 (CTCAE version 4.03) * Known hypersensitivity to any contents of the study drugs * Pregnancy (positive pregnancy test) and/or breast feeding * Any other serious or uncontrolled illness which in the opinion of the investigator makes it undesirable for the patient to enter the trial