NCT07327515

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

A Phase I/II Study of PET/CT-Guided Biological Target Volume Delineation and Dose Optimization for Radioactive Seed Implantation Therapy in Malignant Tumors

• Status: Not Yet Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 90 (estimated)
• Sponsor: Li Min · Academic / Other
• Sex: All
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

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.

Detailed description

This prospective, open-label Phase I/II trial evaluates a molecular-imaging-guided optimization strategy that integrates PET/CT into radioactive seed implantation therapy to improve target delineation accuracy, biological precision, and therapeutic efficacy in malignant solid tumors. Conventional CT-guided planning relies primarily on anatomical visualization and geometric dose coverage but does not incorporate intratumoral biological heterogeneity, which may result in uneven dose distribution and increased risk of local recurrence. To address this limitation, the trial incorporates PET/CT-based biological target volume (BTV) delineation and standardized uptake value (SUV)-driven dose modulation to achieve individualized, biologically optimized treatment planning. Eligible participants with measurable solid tumors suitable for percutaneous implantation are assigned to one of three groups: (1) conventional CT-guided implantation, (2) PET/CT-guided implantation with standard dosing, and (3) PET/CT-guided implantation with biological dose optimization based on metabolic activity quantified by SUV measures. PET/CT is used to identify metabolically active sub-volumes for selective dose escalation while sparing normal tissues, achieved by adjusting seed activity or spatial distribution to deliver intensified irradiation to high-SUV tumor regions. In addition to standard 18F-FDG PET/CT, tumor-specific tracers are evaluated in selected subgroups to enhance lesion visualization and biological characterization, including 18F-PSMA for prostate cancer, 68Ga-FAPI for pancreatic, colorectal, and fibrotic tumors, 18F-FES for ER-positive breast cancer, and 18F-FMISO or 18F-FAZA for hypoxia detection and targeted dose escalation. Primary endpoints include technical success rate, dosimetric superiority, and 6-month local control defined by imaging and clinical criteria. Secondary endpoints include dosimetric parameters (D90, V100, conformity index, homogeneity index), pain relief, quality of life (EORTC QLQ-C30), treatment-related adverse events (CTCAE v5.0), and time-to-event outcomes including progression-free survival (PFS), failure-free survival (FFS), and overall survival (OS). Exploratory analyses evaluate correlations between baseline PET parameters (SUVmax, metabolic tumor volume, total lesion glycolysis), radiomics features, and clinical outcomes, as well as early metabolic response (ΔSUVmax at 4-6 weeks) as a predictor of local control. The central hypothesis is that PET/CT-guided biological optimization will enhance dosimetric conformity, improve local tumor control and survival outcomes, reduce recurrence, and contribute to better symptom relief and quality-of-life measures. Overall, the trial aims to establish a personalized, molecular-imaging-based framework for radioactive seed implantation therapy in malignant solid tumors.

Conditions

• Malignant Tumors

Interventions

Type	Name	Description
PROCEDURE	CT-Guided Radioactive Seed Implantation	CT-guided implantation of 125I radioactive seeds for localized treatment of malignant tumors. The target area is delineated on contrast-enhanced CT images, and seeds are implanted according to a treatment planning system (TPS) with a prescribed dose of about 100 Gy. Post-procedure dosimetry will confirm D90, V100, and V150, as well as organ-at-risk (OAR) dose constraints.
PROCEDURE	PET/CT-Guided Radioactive Seed Implantation	PET/CT-guided 125I seed implantation performed using PET/CT fusion to support anatomical target delineation without SUV-based biological sub-volume definition. A standard uniform-dose treatment plan is implemented, and post-implant dosimetric evaluation is used to confirm target coverage and compliance with organ-at-risk constraints.
PROCEDURE	PET/CT-Guided Radioactive Seed Implantation (Biological Dose Optimization)	PET/CT-guided 125I seed implantation for the treatment of malignant tumors. The biological target volume (BTV) is defined using 18F-FDG PET/CT fused with planning CT to improve target accuracy and tumor coverage. The prescribed dose is approximately 100 Gy. Post-implant verification includes D90, V100, and OAR constraints.
PROCEDURE	Tumor-Specific PET/CT-Guided Radioactive Seed Implantation (PSMA/FAPI Subgroup)	125I seed brachytherapy guided by tumor-specific PET/CT imaging. Tracers such as PSMA (for prostate cancer) and FAPI (for pancreatic, colorectal, and fibrotic tumors) identify biologically active regions for targeted dose escalation. High-uptake areas (SUVmax \> threshold determined by tracer characteristics) receive escalated doses of approximately 120-150 Gy through increased seed density or activity, while normal tissues remain within tolerance limits.

Timeline

• Start date: 2026-01-01
• Primary completion: 2027-06-01
• Completion: 2028-06-01
• First posted: 2026-01-08
• Last updated: 2026-01-08

Locations

1 site across 1 country: China