PET/CT-Guided Biological Target Volume Delineation and Dose Optimization for Radioactive Seed Implantation Therapy in Malignant Tumors

This prospective, open-label Phase I/II trial evaluates a PET/CT-guided planning strategy for radioactive seed implantation therapy in malignant solid tumors. The approach integrates metabolic information from PET/CT into brachytherapy planning to improve the accuracy of biological target volume delineation, enhance dose coverage, and support biologically informed dose delivery. Eligible participants are assigned to one of three arms: conventional CT-guided implantation, PET/CT-guided standard-dose implantation, or PET/CT-guided biologically optimized implantation. All participants undergo image-guided treatment followed by post-implant dosimetric verification and standardized clinical follow-up. Primary endpoints include technical success rate, dosimetric superiority, and 6-month local control. Secondary endpoints include dosimetric indices (D90, V100, conformity index, homogeneity index), pain relief, quality of life (EORTC QLQ-C30), treatment-related adverse events (CTCAE v5.0), progression-free survival (PFS), failure-free survival (FFS), and overall survival (OS). Exploratory analyses will evaluate associations between baseline PET metabolic parameters (SUVmax, metabolic tumor volume) and clinical outcomes, assess the feasibility of SUV-guided dose painting, and compare the performance of tumor-specific tracers (such as PSMA and FAPI) with FDG for target delineation and treatment response prediction. The central hypothesis is that PET/CT-guided planning-particularly when incorporating biological dose optimization-will achieve superior dosimetric performance and improved local control and survival outcomes compared with conventional CT-guided implantation.

Sex

All

Minimum age

18 Years

Inclusion Criteria:

1. Age ≥ 18 years.
2. Pathologically or clinically confirmed malignant tumor (solid tumor, lymphoma, or leukemia with a localized lesion suitable for radioactive seed implantation).
3. Tumor site accessible for image-guided implantation, with a target lesion visible on CT or PET/CT.
4. Life expectancy of at least 6 months.
5. Ability to undergo PET/CT imaging (FDG or tumor-specific tracers such as PSMA or FAPI).
6. Signed written informed consent.

Exclusion Criteria:

1. Pregnant or breastfeeding women.
2. Uncontrolled infection or active systemic inflammatory disease.
3. Severe cardiopulmonary dysfunction that contraindicates interventional procedures (e.g., heart failure, severe COPD).
4. Coagulation disorders (INR \> 1.5 or platelet count \< 50 × 10⁹/L).
5. Known allergy or intolerance to radiopharmaceuticals or iodinated contrast media.
6. Prior radiation therapy overlapping with the planned implantation area.
7. Participation in another clinical trial within the past 30 days that may interfere with study results.
8. Any medical or psychosocial condition considered unsuitable for study participation by the investigators (e.g., poor compliance, unstable clinical status).