125I Seed Implantation Plus Systemic Therapy for Oligoprogressive NSCLC or Colorectal Cancer

This is a prospective, open-label, randomized phase 2 controlled trial enrolling adults with histologically confirmed metastatic NSCLC or colorectal cancer who developed extracranial oligoprogression (≤5 progressive lesions) on PET/CT or CT while receiving at least first-line systemic therapy (including maintenance). Eligible patients will be randomized 1:1 to (1) standard-of-care systemic therapy per treating physician discretion, or (2) image-guided 125I seed implantation to all oligoprogressive lesions plus standard-of-care systemic therapy.

Oligoprogression will be determined by predefined imaging response criteria (RECIST and/or PERCIST, depending on baseline imaging modality), with confirmation by designated study radiologists. Follow-up imaging will be performed at 8 weeks (±2 weeks) after randomization and every 12 weeks (±2 weeks) thereafter to assess disease status. The primary endpoint is progression-free survival measured up to 12 months. Secondary endpoints include overall survival, time to initiation of a new systemic therapy, local control of implanted lesions, safety, and quality of life. Optional exploratory objectives may include circulating tumor DNA dynamics and metabolic PET parameters.

Inclusion criteria

• Age ≥ 18 years.
• Histologically or cytologically confirmed metastatic non-small cell lung cancer (NSCLC) or colorectal cancer (CRC).
• Presence of metastatic disease with extracranial oligoprogression, defined as progression in up to five (≤5) individual lesions on CT or PET/CT imaging, while other known disease sites remain stable or controlled.
• Received at least one prior line of standard systemic anticancer therapy, including maintenance therapy, for metastatic disease.
• All oligoprogressive lesions are technically feasible and considered safe for image-guided 125I seed implantation, as determined by the treating interventional team.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Adequate organ function to undergo interventional procedures and systemic therapy, per institutional standards.
• Ability to understand and willingness to sign written informed consent.

Exclusion criteria

• Pregnancy or breastfeeding.
• Leptomeningeal disease or diffuse central nervous system involvement. Uncontrolled infection or serious medical comorbidities that, in the investigator's judgment, would preclude safe participation or interventional procedures.
• Prior radiotherapy or brachytherapy requiring re-irradiation to the same tumor location planned for 125I seed implantation.
• Known bleeding diathesis or uncorrectable coagulation disorders contraindicating interventional procedures.
• Any other condition that, in the investigator's judgment, would make the patient unsuitable for the study.