This is a prospective, multicenter, randomized, and open-label clinical trial. It is initiated to determine the efficacy of FOLFOX-based, transarterial infusion chemotherapy (TAIC) combined with either cetuximab or bevacizumab for patients with unresectable colorectal cancer (CRC).

Current CRC treatment options include surgical resection, intravenous chemotherapy (IVC), radiation therapy, immunotherapy, and targeted therapy, or a combination of these options. IVC is an important therapy for CRC. Unfortunately, IVC results in broad drug distribution, while achieving with relatively low drug accumulation within the tumor. Compared with IVC, TAIC can increase the local intra-tumoral concentrations of chemotherapeutic agents by intensifying drug delivery into the tumor via super-selective catheterization of the tumor-feeding artery, and meanwhile reduce systematic toxicity. Hepatic artery infusion chemotherapy (HAIC) has been shown to yield significantly better outcomes than conventional transarterial chemoembolization (TACE) or IVC, and is now widely used for primary liver cancer and secondary liver malignancies. Based on these experiences, the investigators hypothesize that TAIC is clinically more effective at the same dose than IVC in the treatment of unresectable CRC. However, there is currently no high-quality evidence from clinical trials to support this hypothesis. To address this gap, the investigators will conduct a prospective study to verify this hypothesis. Eligible patients are those with unresectable CRC, those intolerant to surgical resection, and those with microsatellite instability or microsatellite instability low or proficient mismatch repair CRC. A total of 30 patients will be randomly assigned to the IVC group or TAIC group. Patients in the IVC group will receive the FOLFOX-based IVC with either cetuximab or bevacizumab every two weeks for a total of 8 weeks. Patients in the TAIC group will undergo FOLFOX-based TAIC combined with either cetuximab or bevacizumab on weeks 0 and 4 and will receive FOLFOX-based IVC with either cetuximab or bevacizumab on weeks 2 and 6. The primary endpoints are the objective response rate (ORR) and disease control rate (DCR).

Inclusion Criteria:

1. Age ≥ 18 years;
2. Colorectal cancer confirmed by CT/MRI and colonoscopic biopsy；
3. Patients unfit for surgery due to poor general condition or tumor extent and location;
4. Patients who have not received prior chemotherapy or those who have undergone prior chemotherapy but remain chemosensitive.
5. Adequate haematological, heart, liver and renal functions are required, with the following specific criteria: white blood cell count≥4000/mL, neutrophils≥1500/mm³, platelets≥100×10⁹/L, haemoglobin≥10.0 g/L, total bilirubin 2.0 mg/dL, aspartate aminotransferase 100 IU/L, alanine aminotransferase 100 IU/L, serum creatinine 1.5 mg/dL or creatinine clearance rate≥60 mL/min/body, and urine protein/creatinine<1.
6. Patients have to have an expected life expectancy of ≥3months.
7. All the subjects in this study are required to sign an informed consent form.

Exclusion Criteria:

1. Patients with other primary malignant tumors;
2. Patients with gastrointestinal perforation;
3. Patients are allergic to the antitumor agents;
4. Women who are pregnant, breastfeeding, or planning to become pregnant;
5. Patients who receive other antitumor therapies concurrently, such as chemotherapy, targeted therapy, or radiotherapy;
6. Patients with MSI-H/dMMR CRC；
7. Patients for whom participation in the study is deemed to be inappropriate by the doctor in charge and/or the investigator for any other reasons.

At present, this study remains in the active implementation phase. Given that individual participant data (IPD) contains sensitive personal privacy information of research subjects, the investigators will not share the IPD with external researchers temporarily, in order to strictly comply with ethical requirements and fully protect the legitimate rights and interests of study participants.