In this clinical trial, patients with gastric and gastroesophageal junction adenocarcinoma will be included. Treatment with curative intent will be given with chemotherapy for 4 cycles with fluorouracil, oxaliplatin and irinotecan preoperatively followed by surgery, and then additionally 4 cycles of the same chemotherapy postoperatively. The standard treatment today is preoperative treatment with fluorouracil and oxaliplatin pre-and postoperatively. The rationale for this trial is, that the addition of irinotecan might improve treatments results.

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