FAPI in Rectal Cancer TNT

Study Overview
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Brief Summary
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The goal of the trial is to observe the changes of 68Ga FAPI signal before and after total neoadjuvant therapy for rectal cancers, and the correlation between the image parameters, immune checkpoints expression as well as the patient outcome. The trial will recruit patients with biopsy-confirmed rectal cancer aged 18 years old or older, with WHO/ECOG Performance Status 0-1, and eligible for total neoadjuvant therapy at the clinicians' discretion. After signing the informed consent, the participants will undergo a standard staging work-up if not already done, including colonoscopy and cross-sectional images such as CT, MR, and FDG-PET. Kidney function (by serum creatinine) and liver function (by serum alanine aminotransferase) will also be assessed. Only patients with stage II-III rectal cancer will be recruited. If patients meet the inclusion and exclusion criteria, they will undergo the first 68Ga-FAPI PET within 30 days before the beginning of total neoadjuvant therapy. At 22-24 weeks into the TNT, follow-ups for response evaluation will be conducted, including colonoscopy and cross-sectional images such as CT, MR, and FDG-PET. The second 68Ga-FAPI PET will be performed within one month of these exams. Afterward, participants will either undergo surgery or have image follow-ups every 3 months. The participants will be followed up for up to 2 years after the second 68Ga-FAPI PET, and immunochemical staining with CD47, CD73, PD-L1, and FAP on the biopsy or surgical specimens will be performed in one batch to avoid batch-to-batch variation.

Official Title
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68Ga FAPI in Total Neoadjuvant Therapy of Rectal Cancer

Conditions
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Rectal Neoplasms Malignant

Intervention / Treatment
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* Radiation: Ga-68 FAPI


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Biopsy proven newly detected adenocarcinoma of the rectum Clinical stage II-III rectal cancer Aged at least 18 years. No upper age limit. WHO/ECOG Performance Status 0-1 Eligible for total neoadjuvant therapy Exclusion Criteria: Distant metastases found on either CT, MR or FDG-PET Prior anticancer therapy for colorectal cancer Prior radiotherapy of the pelvic region Other concurrent antineoplastic therapy Major surgery within the last 4 weeks prior to inclusion Subjects pregnant or breast feeding Serious concurrent diseases not compatible with study entry, including active, uncontrolled infections, active, disseminated coagulation disorder, clinically significant cardiovascular disease (including myocardial infarction, unstable angina, symptomatic congestive heart failure, serious uncontrolled cardiac arrhythmia within 6 months before enrolment) Neurologic or psychiatric disorders including dementia, uncontrolled seizures, substance abuses, severe depression Prior or concurrent malignancy within 3 years prior to enrolment (except non-melanoma skin cancer or cervical carcinoma FIGO stage 0-1) Allergic to contrast agents or to the main ingredients or excipients of the experimental radiopharmaceutical 68Ga FAPI, including acetate, ascorbic acid and normal saline Those deemed unsuitable for participation in the trial by the investigators.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| observation<br>Ga-68 FAPI study before and during TNT | Radiation: Ga-68 FAPI<br>* FAPI PET scans will be performed in addition to other staging/restaging work-up<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change of FAPI SUV | To compare the FAPI uptake after TNT | before TNT & 22-24wk into TNT | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation of FAPI SUV | FAPI SUV will be correlated with (1) 2-year disease-free survival (DFS), (2) 2-year local regional recurrence (LRR), (3) 2-year total mesorectal excision (TME)-free survival, (4) 2-year overall survival (OS), (5) overall complete response (CR) rate, and (6) immune checkpoint protein expression including CD47, CD73, PD-L1, and FAP | 2 years after recruitment |