The percutaneous radiofrequency ablation (RFA) is guided by ultrasound imaging to target and locate the tumor, and the ablation electrode needles are inserted into the tumor foci, leading to the death of the tumor cells through direct thermal effect. In recent years, many clinical studies have confirmed that RFA is a minimally invasive, safe and effective local treatment for liver tumors, which has been widely used and studied worldwide. This study is for patients with intrahepatic multifocal recurrence after surgery for liver metastasis of colorectal cancer. Systemic therapy with/without radiofrequency ablation will be performed of intrahepatic lesions. The feasibility, efficacy and safety of the treatment strategy will be evaluated and analyzed through follow-up, which will provide a new treatment mode and a basis for clinical decision-making for patients with multiple lesions of progressive colorectal cancer.

For patients with multiple intrahepatic metastatic lesions, who are not suitable for or refuse to undergo surgical re-resection, explore the feasibility of a modality treatment of radiofrequency batch therapy combined with systemic therapy. Firstly, 2-4 cycles of systemic therapy should be performed, and the response to treatment should be evaluated by enhanced CT/MRI combined with multimodal ultrasonography, and radiofrequency ablation should be performed for patients who have effective systemic therapy. Before radiofrequency ablation treatment, relevant hematological tests, such as blood routine, biochemistry, coagulation function, etc., were performed to ensure that the enrollment criteria were met. For patients who do not meet the enrollment criteria, radiofrequency ablation treatment will be postponed and clinical treatment will be performed until the enrollment criteria are met, and those patients who cannot meet the enrollment criteria will be withdrawn from the study. Secondly, the 2-6 intrahepatic lesions for the first radiofrequency ablation were confirmed according to the ultrasound model and other clinical factors. After radiofrequency treatment, 1-2 cycles of systemic treatment were carried out, and after effective evaluation, radiofrequency ablation was performed again for 2-6 foci (the selection criteria were the same as the above), and so on, with a maximum of 3 times of ablations, to ablate all the visible foci as far as possible, and to achieve a basically no evidence of disease in the liver. Systemic therapy was separated from radiofrequency ablation therapy by 1 week to minimize the impact of treatment side effects. In the control group, patients would be treated with systemic therapy alone, without localized treatment.

Enhanced CT/MRI will be performed 1 month after radiofrequency ablation treatment to evaluate the effectiveness of the technique. Ultrasound/contrast-enhanced ultrasound imaging, enhanced CT/MRI, laboratory tests (hematology, blood biochemistry, tumor markers, etc.), electrocardiogram will be performed every 3 months within 2 years after treatment. Ultrasound/contrast-enhanced ultrasound imaging, laboratory tests, electrocardiogram will be performed every 3 months and enhanced CT/MRI every 6 months after 2 years of treatment.

Due to the large number of lesions treated with radiofrequency, the occurrence of post-radiofrequency complications is closely monitored, as well as the effect on the patient's hepatic and renal function after radiofrequency ablation. As radiofrequency ablation may reduce the times of systemic therapy, it may reduce the toxic side effects of systemic therapy. Patients in both groups were tested regularly, asked about their condition, underwent physical examination, recorded vital signs and laboratory indicators, electrocardiograms, adverse events such as drug side effects and complications of radiofrequency therapy.