Comparison of [68Ga]Ga-CTR-FAPI and 18F-FDG PET/MRI for Lymph Node Staging in Rectal Cancer (PKUCH-R12)

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

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Rectal Cancer; Lymph Node Metastases; PET / MR
• Intervention / Treatment: Diagnostic test: PET/MRI with 18F-FDG and [68Ga]Ga-CTR-FAPI

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).

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Minghe Zhao; Phone Number: 0086-15600896700; Email: dzhao3163@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Rectal Cancer Patients; Patients with confirmed middle to high rectal adenocarcinoma who are scheduled for radical surgery.	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).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sensitivity and Specificity of Lymph Node Metastasis Detection	Comparison of the sensitivity and specificity of [68Ga]Ga-CTR-FAPI and 18F-FDG PET/MRI in determining lymph node metastasis at both the individual lymph node level and the patient level. Sensitivity is defined as the proportion of imaging-positive and pathology-positive nodes out of all pathology-positive nodes. Specificity is defined as the proportion of imaging-negative and pathology-negative nodes out of all pathology-negative nodes.	Up to 30 days post-surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
False Positive and False Negative Rates	Analysis of the false positive and false negative rates of FAPI and FDG imaging, exploring underlying pathological bases such as inflammation or micrometastasis.	Up to 30 days post-surgery
Correlation Between Radiomics Features and Tumor Microenvironment	Extraction of lymph node radiomics features to evaluate their association with tumor microenvironmental markers, determined via automatic immunohistochemistry scoring.	Up to 30 days post-surgery

Collaborators and Investigators

• Sponsor: Peking University Cancer Hospital & Institute

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: April 20, 2026
• First Submitted That Met QC Criteria: April 20, 2026
• First Posted (Actual): April 27, 2026

Study Record Updates

• Last Update Posted (Actual): May 4, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: PET/MR; 18F-FDG; Radiomics; [68Ga]Ga-CTR-FAPI; Lymph Node Staging
• Additional Relevant MeSH Terms: Pathologic Processes; Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Colorectal Neoplasms; Intestinal Neoplasms; Rectal Diseases; Neoplastic Processes; Neoplasm Metastasis; Pathological Conditions, Signs and Symptoms; Rectal Neoplasms; Lymphatic Metastasis
• Other Study ID Numbers: PKUCH_R12

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No