Image-Guided 125I Seed Implantation Plus Standard Systemic Therapy for Patients With Multiple Metastatic Lesions

Inclusion Criteria:

* Age ≥ 18 years.
* Histologically or cytologically confirmed malignant solid tumor with metastatic disease.
* Presence of more than five and up to ten (6-10) extracranial metastatic lesions, identified on CT or PET/CT imaging and assessable by RECIST version 1.1 (and/or PERCIST when PET imaging is used).
* At least one metastatic lesion considered suitable for image-guided iodine-125 (125I) seed implantation according to institutional assessment.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.
* Adequate organ function to undergo interventional procedures and systemic therapy, as determined by institutional standards.
* Ability to understand and willingness to provide written informed consent.

Exclusion Criteria:

* Diffuse or unstable central nervous system involvement, including leptomeningeal disease or uncontrolled/symptomatic brain metastases requiring immediate local intervention.
* Medical conditions that preclude safe interventional procedures, including uncontrolled infection, severe cardiopulmonary dysfunction, or other serious systemic illness, as judged by the investigator.
* Contraindications to percutaneous implantation, such as uncorrectable coagulation disorders, high bleeding risk, lack of a safe needle path, or unacceptable risk to critical organs.
* Pregnancy or breastfeeding.
* Inability to provide informed consent or comply with study procedures, due to severe psychiatric illness, cognitive impairment, or other limiting conditions.
* Any other condition that, in the investigator's judgment, would make the patient unsuitable for study participation or compromise patient safety or study integrity.