68Ga-SorB PET/CT Imaging in Patients With Solid Tumors

Background Sortilin is a type I transmembrane receptor belonging to the VPS10 receptor family. It is highly expressed in a variety of malignancies, including melanoma, hepatocellular carcinoma, lung cancer, pancreatic cancer, breast cancer, and ovarian cancer, while showing relatively low expression in most normal tissues. Due to its tumor-specific expression pattern and efficient receptor-mediated internalization, Sortilin has emerged as a promising molecular target for cancer imaging and targeted theranostic applications.

Although ^18F-FDG PET/CT is widely used for oncologic imaging, its diagnostic performance may be limited by nonspecific uptake in inflammatory lesions, resulting in false-positive findings. Therefore, a more tumor-specific PET tracer may improve lesion detection and diagnostic accuracy.

Study Design This is a prospective, single-center, open-label, exploratory diagnostic imaging study designed to evaluate the clinical performance of the novel Sortilin-targeted PET radiotracer ^68Ga-SorB. Approximately 40-50 adult patients with confirmed or suspected melanoma, hepatocellular carcinoma, lung cancer, pancreatic cancer, breast cancer, pancreatic cancer, or ovarian cancer will be enrolled. All participants will undergo ^68Ga-SorB PET/CT imaging according to the study protocol. Standard-of-care ^18F-FDG PET/CT performed within the predefined time window will be used as the comparator whenever available.

Histopathological findings and/or clinical and imaging follow-up will serve as the reference standard for evaluating diagnostic performance.

Study Objectives The primary objectives are to evaluate the safety and tolerability of ^68Ga-SorB, assess imaging feasibility, and characterize tracer biodistribution and tumor uptake using quantitative PET parameters, including SUVmax and tumor-to-background ratio (TBR).

Secondary exploratory objectives include comparison of lesion detection between ^68Ga-SorB PET/CT and ^18F-FDG PET/CT, estimation of diagnostic sensitivity, specificity, and accuracy, evaluation of tracer uptake across different tumor types, assessment of the association between Sortilin expression and imaging parameters, and exploration of the potential clinical value of ^68Ga-SorB PET/CT in tumor diagnosis and staging.

Study Significance This exploratory clinical study is expected to generate preliminary evidence regarding the safety, feasibility, and diagnostic performance of ^68Ga-SorB PET/CT in patients with solid tumors. The results may support further multicenter validation studies and facilitate the clinical development of Sortilin-targeted molecular imaging and future theranostic strategies.

Inclusion criteria

• - Adults aged 18 to 75 years.
• Histologically confirmed or clinically suspected melanoma, hepatocellular carcinoma, lung cancer, breast cancer, pancreatic cancer, or ovarian cancer.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Adequate hematologic, hepatic, renal, and coagulation function:
• White blood cell count ≥ 4.0 × 10^9/L or absolute neutrophil count ≥ 1.5 × 10^9/L;
• Platelet count ≥ 100 × 10^9/L;
• Hemoglobin ≥ 90 g/L;
• PT or APTT ≤ 1.5 × upper limit of normal (ULN);
• Total bilirubin ≤ 1.5 × ULN;
• ALT and AST ≤ 2.5 × ULN (or ≤ 5 × ULN for participants with liver metastases);
• ALP ≤ 2.5 × ULN (or ≤ 4.5 × ULN for participants with bone or liver metastases);
• Blood urea nitrogen and serum creatinine ≤ 1.5 × ULN.
• Normal cardiac function.
• Estimated life expectancy of at least 12 weeks.
• Willing and able to comply with study procedures and follow-up.
• At least one measurable target lesion according to RECIST version 1.1.
• Participants of childbearing potential agree to use effective contraception during the study and for 3 months after PET/CT imaging.
• Clinically indicated to undergo 18F-FDG PET/CT for tumor evaluation.
• Able to understand the study procedures and provide written informed consent.

Exclusion criteria

• Pregnant or breastfeeding women.
• Severe dysfunction of major organs (including heart, liver, or kidney) that, in the investigator's judgment, would make participation inappropriate.
• Inability to tolerate PET/CT imaging or complete study follow-up.
• Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study.