Post-resection/Ablation Chemotherapy in Patients With Metastatic Colorectal Cancer (FIRE-9 - PORT / AIO-KRK-0418)

Inclusion Criteria: 1. Patient's signed informed consent. 2. Patient's age ≥18 years at the time of signing the informed consent. 3. Histologically confirmed adenocarcinoma of the colon or rectum. 4. Resected (R0 or R1) and/or effectively treated metastases (all techniques allowed) of colorectal cancer within 3-10 weeks before randomization (earlier randomisation allowed if at least 3 weeks interval between intervention and treatment start is guaranteed) AND resected primary tumor (synchronous or metachronous). In cases of synchronous metastases the interval of 3-10 weeks might be calculated following the removal of the primary tumor if this intervention was the last to address all tumor lesions. 5. Absence of significant active wound healing complications (if applicable) at randomization. Resolved wound healing complications after resection/ablation are acceptable for inclusion into the trial. 6. No radiographic evidence of active metastatic disease at study entry in a CT and/or MRI scan not older than 10 weeks prior randomization. Pre-surgery/ablation images are eligible for the study if all lesions have been addressed in the interval. 7. ECOG performance status 0-2. 8. Adequate bone marrow, hepatic and renal organ function, defined by the following laboratory test results: * Absolute neutrophil count \>= 1.5 x 109/L (1500/µL) * Hemoglobin ≥ 80 g/L (8 g/dL) * Platelet count ≥ 100 x109/L (100000/µL) without transfusion * Total serum bilirubin of ≤ 1.5 x upper limit of normal (ULN) * Aspartate aminotransferase (AST/GOT) ≤ 3.0 × ULN. * Calculated glomerular filtration rate (GFR) according to Cockcroft-Gault formula or according to MDRD ≥ 50 mL/min or serum creatinine ≤ 1.5 x ULN 9. Patients without anticoagulation need to present with an INR \< 1.5 x ULN and PTT \< 1.5 x ULN. Patient with prophylactic or therapeutic anticoagulation are allowed into the trial. 10. Proficient fluorouracil metabolism as defined: 1. Prior treatment with 5-FU or capecitabine without unusual toxicity or 2. If tested, normal DPD deficiency test according to the standard of the study site or 3. If tested, in patients with DPD deficiency test with a CPIC activity score of 1.0-1.5 fluoropyrimidine/capecitabine dosage should be reduced by 50% 11. For women of childbearing potential (WOCBP): negative pregnancy test within 14 days before randomization and agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods with a failure rate of \< 1% per year during the treatment period and for at least 9 months after the last dose of Oxaliplatin or for at least 6 months after the last dose of all other study treatment. A woman is considered to be of childbearing potential if she is post-menarcheal, has not reached a postmenopausal state (≥ 12 continuous months of amenorrhea with no identified cause other than menopause), and has not undergone surgical sterilization (removal of ovaries and/or uterus). Examples of contraceptive methods with a failure rate of \< 1% per year include bilateral tubal ligation, male partner's sterilization, hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterine devices. For men: With female partners of childbearing potential, men must remain abstinent or use a condom plus an additional contraceptive method that together result in a failure rate of \< 1% per year during the treatment period and for 6 months after the last dose of study treatment. Men must refrain from donating sperm during this same period. Exclusion Criteria: 1. Treatment of metastases greater than 3 cm with radio-frequency/microwave ablation within 24 months prior to study entry if applicable. 2. Treatment of metastases greater than 5 cm with radiation (stereotactic/ brachytherapy) within 24 months prior to study entry if applicable. 3. Any previous systemic therapy is allowed for inclusion into the trial. However, if previous oxaliplatin-containing chemotherapy at any time for metastatic or localized disease was carried out, the inclusion into the trial is permitted under the condition, that 1. A total duration of oxaliplatin-based therapy of six months (i.e. 12 cycles of FOLFOX / FOLFOXIRI or 8 cycles CAPOX) is not exceeded - including therapy within the FIRE-9/PORT trial 2. If already more than three months of oxaliplatin-based therapy (i.e. \>6 cycles of FOLFOX / FOLFOXIRI or \>4 cycles CAPOX) was used, the study therapy should be started with an irinotecan-based regimen (i.e. FOLFIRI or FOLFOXIRI) However, in the case of FOLFOXIRI therapy in the trial, the above mention regulation concerning the total dosing of oxaliplatin still applies (i.e. 12 cycles of FOLFOX / FOLFOXIRI or 8 cycles CAPOX should not be exceeded - including therapy within the FIRE-9/PORT trial). 4. New York Heart Association Class III or greater heart failure by clinical judgement. 5. Myocardial infarction within 6 months prior to randomization; percutaneous transluminal coronary angioplasty (PTCA) with or without stenting within 6 months prior to randomization. 6. Unstable angina pectoris. 7. Unstable cardiac arrhythmia \> grade 2 NCI CTCAE despite anti-arrhythmic therapy. 8. Ongoing toxicities \> grade 2 NCI CTCAE 9. Active uncontrolled infection by investigator's perspective. 10. Severe chronic non-healing wounds, ulcerous lesions or untreated bone fracture. 11. Known hypersensitivity to 5-FU, folinic acid, irinotecan, oxaliplatin or capecitabine or to any of the other excipients listed in section 6.1 of the corresponding SmPC. 12. Recent or concomitant treatment with brivudine. 13. Peripheral sensitive neuropathy with functional impairment (\> grade 1 acc. to CTCAE version 5.0 (see appendix 2)). 14. Inflammatory bowel disease and/or bowel obstruction. 15. Simultaneous application of Johannis herbs preparations. 16. Pernicious or other megaloblastic anemia caused by vitamin B12 deficiency. 17. Major surgical procedur