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

Overview

Patients with more than five and up to ten metastatic lesions often have limited tolerance for surgery, radiotherapy, or thermal ablation because of cumulative treatment burden or expected toxicity. In this setting, systemic therapy alone frequently remains the primary treatment option. This prospective, open-label, randomized phase 2 study evaluates whether image-guided iodine-125 (125I) seed implantation, when added to standard-of-care systemic therapy, can improve disease control compared with standard systemic therapy alone in patients with multiple metastatic lesions. Clinical outcomes including progression-free survival, overall survival, safety, and quality of life will be prospectively assessed.

This is a prospective, open-label, randomized phase 2 interventional study designed to evaluate the efficacy and safety of image-guided iodine-125 (125I) seed implantation in combination with standard-of-care systemic therapy compared with standard systemic therapy alone in patients with multiple metastatic lesions. Patients with more than five and up to ten extracranial metastatic lesions often have limited tolerance for surgery, radiotherapy, or thermal ablation due to cumulative treatment burden or expected toxicity, and in this setting, systemic therapy alone frequently remains the only treatment option. This study therefore explores the potential role of image-guided radioactive seed implantation as an additional local treatment strategy for this patient population. After eligibility confirmation and baseline assessments, participants will be randomly assigned in a 1:1 ratio to receive either standard-of-care systemic therapy alone or image-guided 125I seed implantation plus standard-of-care systemic therapy. Randomization will be performed using a predefined allocation scheme, and the study is conducted in an open-label manner due to the interventional nature of the procedure. The primary endpoint of the study is progression-free survival (PFS), defined as the time from randomization to disease progression or death from any cause, whichever occurs first. Secondary endpoints, aligned with prior randomized studies of metastasis-directed therapy, include overall survival, time to initiation of a new systemic therapy, treatment-related adverse events, and patient-reported quality of life. Exploratory objectives include descriptive analyses of patterns of disease progression. Participants assigned to the experimental arm will undergo image-guided 125I seed implantation targeting multiple metastatic lesions, performed under CT guidance (with PET/CT fusion planning when clinically indicated) according to institutional standards. Systemic anticancer therapy will be administered in both study arms at the discretion of the treating physician in accordance with current clinical guidelines. All participants will undergo scheduled clinical and imaging follow-up, with disease progression assessed using RECIST version 1.1 and/or PERCIST criteria.