This is a prospective, multicenter, randomized controlled, phase II study. It is expected to enroll 229 patients and aims to evaluate the efficacy and safety of FOLFOX8 versus mFOLFOX6 combined with bevacizumab or cetuximab as first-line treatment for unresectable metastatic colorectal cancer. The primary objective is to assess progression-free survival (PFS) of the patients. Secondary objectives include assessment of objective response rate (ORR), overall survival (OS), safety, and other outcomes.

Levofolinic Acid For Injection is the first approved class 2.1 sodium levoleucovorin formulation in China. It contains only the active l-isomer of levoleucovorin, with an equivalent dose half that of leucovorin. As a sodium salt, it has higher solubility, is compatible with 5-FU, and allows concurrent infusion. The FOLFOX8 regimen is based on mFOLFOX6 and takes advantage of the sodium salt formulation of Levofolinic Acid For Injection by changing the traditional sequential infusion of 5-FU and calcium levoleucovorin to concurrent infusion of Levofolinic Acid For Injection and 5-FU, thereby prolonging the duration of synergistic action and enhancing overall efficacy. It is expected to further delay disease progression in patients with colorectal cancer.

This study is a prospective, multicenter, randomized controlled phase II trial. A total of 229 patients will be enrolled and randomly assigned to the experimental group (FOLFOX8) or the control group (mFOLFOX6). Targeted therapy (bevacizumab or cetuximab) will be selected based on the patient's RAS mutation status and tumor location. Treatment will be administered every two weeks. Before and after each treatment cycle, patients will undergo routine clinical examinations including blood tests. A maximum of 12 cycles will be given, and patients without disease progression will enter the maintenance phase. Tumor assessments will be performed every 8 weeks after the start of treatment (based on RECIST V1.1 criteria), and concomitant medications and adverse events will be recorded.

The primary endpoint of this study is progression-free survival (PFS). Secondary endpoints include objective response rate (ORR), overall survival (OS), safety, and the impact of the treatment regimen on infusion time.

Inclusion Criteria:

1. Age ≥ 18 years, male or female.
2. ECOG performance status 0-2.
3. Histologically or cytologically confirmed unresectable metastatic colorectal cancer with no prior treatment for unresectable or metastatic disease.
4. Adequate organ function: Hb ≥ 70 g/L; WBC ≥ 3.0×10⁹/L; NEUT ≥ 1.5×10⁹/L; PLT ≥ 75×10⁹/L; AST and ALT ≤ 3× ULN; sCr ≤ 2× ULN; TBIL ≤ 2× ULN.
5. Expected survival > 3 months.

Exclusion Criteria:

1. Known allergy to the study drug(s) and/or their excipients.
2. Contraindications to chemotherapy.
3. Patients with MSI-H or dMMR colorectal cancer.
4. Patients with BRAF mutation.
5. Pregnant or breastfeeding women.
6. History of any second malignancy within 2 years prior to randomization, except for cured localized tumors such as basal cell carcinoma of the skin, squamous cell carcinoma of the skin, superficial bladder cancer, carcinoma in situ of the prostate, cervical carcinoma in situ, or breast carcinoma in situ, which are allowed for enrollment.
7. Patients with systemic medical or psychiatric disorders that make them unsuitable for chemotherapy.
8. Patients deemed unsuitable for enrollment in this study by the investigator's judgment.
9. Participation in another clinical trial of an investigational drug within 4 weeks prior to randomization.