Recent pre-clinical data provide strong evidence that short-term starvation before the administration of cytostatic drugs for the chemotherapy of solid tumors leads to significantly higher efficacy and lower toxicity levels. However, these findings have so far not been validated in patients. The aim of this trial is to provide first clinical evidence regarding the impact of pre-chemotherapeutic short-term starvation on response to therapy (primary endpoint). Additionally, progression-free survival, adverse events, and overall survival will be monitored (secondary endpoints). In perspective, short-term starvation before chemotherapy could represent a simple and secure way to improve both efficacy and tolerance of chemotherapies at low cost.

Inclusion Criteria:

1. Patient (male/female) ≥ 18 years of age

2. Written informed consent obtained prior to any trial specific procedure

3. Patient suffering from gastrointestinal tumors: Cholangiocarcinoma (CC), Pancreatic ductal adenocarcinoma (PDAC), Colorectal Cancer (CRC), Gastric Cancer (GC)/ Adenocarcinoma of the Esophagogastreal Junction (AEG) / Esophagus cancer (EC).

4. Planned to receive palliative chemotherapy

5. No prior palliative chemotherapy

6. ECOG performance status of 0 or 1

7. Life expectancy of 12 weeks or more

8. Adequate hematological parameters, as demonstrated by:

   • Hemoglobin > 9.0 g/dl (5.6 mmol/l)
   • WBC ≥ 3.0 x 109/l
   • ANC ≥ 1500/mm³
   • Platelets ≥ 75 x 109/l
   • S-creatinine ≤ 1.5 mg/dl (132 µmol/l)

Exclusion Criteria:

1. Underweight (BMI < 18.5)
2. Dysphagia
3. Insulin-dependent diabetes mellitus
4. Renal failure requiring hemo- or peritoneal dialysis
5. Pregnant or breast-feeding women
6. Drug/alcohol abuse