Comparison of [68Ga]Ga-CTR-FAPI and 18F-FDG PET/MRI for Lymph Node Staging in Rectal Cancer

Official title

Comparison of the Diagnostic Efficacy of [68Ga]Ga-CTR-FAPI PET/MRI and 18F-FDG PET/MRI for Lymph Node Metastasis in Middle to High Rectal Cancer

Overview

This is a prospective, single-center, diagnostic study designed to compare the accuracy of \[68Ga\]Ga-CTR-FAPI PET/MRI and \[18\]F-FDG PET/MRI for the detection of lymph node metastasis in patients with initially untreated, resectable middle to high rectal cancer. The study aims to evaluate whether \[68Ga\]Ga-CTR-FAPI PET/MRI provides higher sensitivity and specificity than traditional 18F-FDG PET/MRI at both the patient level and the lymph node level.

Detailed description

Accurate preoperative staging of colorectal cancer is crucial for formulating treatment plans and improving patient prognosis. While conventional MRI and 18F-FDG PET/MRI are utilized, they face limitations such as false positives due to inflammatory lymph nodes or fibrotic scars. Fibroblast activating protein inhibitor (FAPI) specifically targets tumor-associated fibroblasts, potentially reducing false-positive rates by avoiding non-specific uptake in inflammatory areas.

This study aims to cross-validate the diagnostic efficacy of these two probes through a precise imaging-pathology matching technique. All enrolled patients will sequentially undergo both \[68Ga\]Ga-CTR-FAPI PET/MRI and 18F-FDG PET/MRI within 30 days prior to radical surgery. Following surgery, fresh mesorectal specimens will be precisely sectioned and matched to preoperative anatomical imaging maps. By leveraging a well-established node-by-node matching and identification methodology with high accuracy, this study ensures the execution of spatial correlation between preoperative radiologic imaging and postoperative microscopic pathology. Through mapping individual lymph nodes, the study will analyze the root causes of false positives and negatives, and extract radiomics features to evaluate their correlation with the tumor microenvironment (e.g., fibroblast density, Ki-67 index).

Interventions

• Diagnostic test PET/MRI with 18F-FDG and [68Ga]Ga-CTR-FAPI
  Diagnostic Test: 18F-FDG PET/MRI Description: Patients receive an intravenous injection of 18F-FDG (3.7-5.5 MBq/kg). Diagnostic Test: \[68Ga\]Ga-CTR-FAPI PET/MRI Description: Patients receive an intravenous injection of \[68Ga\]Ga-CTR-FAPI (1.8-3.7 MBq/kg).

Primary outcome measures

• Sensitivity and Specificity of Lymph Node Metastasis Detection [Time frame: Up to 30 days post-surgery]

Secondary outcome measures (2)

• False Positive and False Negative Rates [Time frame: Up to 30 days post-surgery]
• Correlation Between Radiomics Features and Tumor Microenvironment [Time frame: Up to 30 days post-surgery]

Eligibility criteria

Inclusion criteria

• Confirmed rectal adenocarcinoma by pathological biopsy.
• Lower margin of the tumor is ≥ 5 cm and ≤15 cm from the anal verge.
• Planned to undergo radical surgery.
• ECOG performance status score ≤ 2.
• Patient is willing to undergo PET/MRI examination.

Exclusion criteria

• History of pelvic radiotherapy or chemotherapy.
• Concurrent with other malignant tumors or active infections.
• Pregnant or unable to sign the informed consent form.
• Claustrophobia or inability to tolerate MRI examinations due to other reasons.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

N/A

Model

Single group

Masking

Open label

Primary purpose

Diagnostic

Study locations

Center list to be confirmed — check the primary protocol.

Identifiers

NCT: NCT07552207 · PKUCH_R12

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗