Lesion-Allocated Therapy for Multiple Metastases and Tumor-Zoned Treatment for Bulky Tumors: A Phase II Study of Iodine-125 Seed Implantation Combined With Cryoablation in High-Burden Metastatic Disease

Summary

This open-label, randomized Phase II trial evaluates whether a strategy-based, multimodal local treatment approach improves local control compared with single-modality local therapy in patients with high-burden metastatic disease characterized by multiple metastases and at least one bulky lesion.

In the experimental arm, prespecified target lesions are prospectively allocated to either iodine-125 (125I) seed implantation or cryoablation using protocol-defined anatomic and technical suitability criteria, and at least one bulky index lesion is treated using a tumor-zoned approach (e.g., core debulking with cryoablation and peripheral/high-risk margin control with 125I seeds) under predefined organ-at-risk constraints. The control arm treats all prespecified target lesions with a single local modality (either 125I seed implantation alone or cryoablation alone), with standardized supportive care and follow-up.

The primary objective is to determine whether the "lesion allocation plus tumor zoning" strategy can improve local control of treated target lesions with acceptable safety. Imaging-based efficacy endpoints are evaluated using protocol-defined criteria with standardized blinded independent imaging review. Key secondary endpoints include local progression-free survival of the bulky index lesion, overall response rate (RECIST), progression-free survival, time to systemic progression (including new lesions), overall survival, tumor-burden reduction metrics, technical success, and re-intervention rates. Safety is assessed throughout the study using CTCAE v5.0, including monitoring for procedure-related and radiation-related complications. Exploratory analyses assess dosimetry-outcome relationships, zonal response patterns within bulky lesions, imaging/radiomics biomarkers, and peripheral blood biomarker dynamics.

Conditions

• High-Burden Metastatic Solid Tumors

Interventions

PROCEDURE

Iodine-125 (125I) Seed Implantation (Low-Dose-Rate Brachytherapy)

Image-guided percutaneous implantation of 125I radioactive seeds into prespecified target lesions according to protocol-defined treatment planning and organ-at-risk constraints. Seed number and distribution are determined by pre-implant planning to achieve protocol-specified target coverage, with post-implant verification imaging and dosimetry as required.

PROCEDURE

cryoablation

Image-guided percutaneous cryoablation of prespecified target lesions using standardized probe placement and freeze-thaw cycles per protocol. The ablation zone is planned to achieve protocol-defined tumor coverage while maintaining safety margins to adjacent critical structures, with intraprocedural monitoring and post-procedure imaging assessment.

OTHER

Lesion Allocation and Tumor Zoning Strategy

Protocol-defined decision rules assign each prespecified metastatic target lesion to 125I seed implantation or cryoablation based on anatomic and technical suitability criteria. For at least one bulky index lesion, a tumor-zoned approach is applied (e.g., core debulking with cryoablation and peripheral/high-risk margin control with 125I seeds) under predefined organ-at-risk constraints and quality assurance requirements.

Sponsors & Collaborators

• Li Min

  lead OTHER

Principal Investigators

• Min Li · The 960th Hospital of People's Liberation Army (PLA)

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-02-28

Primary Completion

2027-07-01

Completion

2028-07-01

Countries

• China

Study Locations