Preoperative Abdominal Enhanced CT, 18F-FDG PET/CT and 68Ga-FAPI PET/CT in Peritoneal Carcinomatosis of Gastric Cancer

Study Overview
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Brief Summary
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This study aims to explore the value of 68Ga-FAPI PET/CT in the diagnosis of gastric cancer peritoneal carcinomatosis in high-risk patients compared with conventional abdominal enhanced CT and 18F-FDG PET/CT. The patients with gastric adenocarcinoma (cT4/N+/M0-1) will be studied.

Detailed Description
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After being informed about the study and potential risks, all patients giving written informed consent will receive 68Ga-FAPI PET/CT on the 2nd day to 1st week of 18F-FDG PET/CT. On PET/CT, omentum, peritoneum, and mesenteric lesions with increased radioactive uptake are defined as suspicious peritoneal carcinomatosis. The number of these positive lesions, the maximum standardized uptake value (SUVmax), median and range will be recorded. Subsequently, the patients will undergo laparoscopic exploration, and if radical resection is assessed, radical gastrectomy (D2 lymph node dissection) will be performed. If a radical resection is not feasible, for patients with peritoneal carcinomatosis detected, one metastasis will be taken for rapid frozen diagnosis. After the peritoneal carcinomatosis is confirmed, the metastases seen under laparoscopy will be matched with the suspicious peritoneal carcinomatosis on the three preoperative imaging examinations. The intraoperative findings are used as the gold standard to compare the detection efficiency of the three imaging examinations for peritoneal carcinomatosis. Patients with unresected tumors will receive 4 cycles of conversion therapy or neoadjuvant therapy. After the treatment, 18F-FDG PET/CT and 68Ga-FAPI PET/CT will be performed again. If necessary, patients will be subjected to a second laparoscopic exploration, and radical gastrectomy (D2 lymph node dissection) will be performed for appropriate patients. If a radical resection is still not feasible, for patients with peritoneal carcinomatosis detected, biopsy of metastases will be performed if necessary.

Official Title
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Preoperative Abdominal Enhanced CT, 18F-FDG PET/CT and 68Ga-FAPI PET/CT to Detect Peritoneal Carcinomatosis in High-Risk Patients With Gastric Cancer: A Prospective, Single-Center, Comparative Study

Conditions
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Enhanced CT, 18F-FDG PET/CT, 68Ga-FAPI PET/CT, Gastric Cancer, Peritoneal Carcinomatosis

Intervention / Treatment
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* Diagnostic Test: 68Ga-FAPI PET/CT scan


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age from 18 to 75 years Primary gastric adenocarcinoma (papillary, tubular, mucinous, signet ring cell, or poorly differentiated) confirmed pathologically by endoscopic biopsy The clinical tumor stage before PET/CT scan was evaluated as cT4/N+/M0-1, according to the American Joint Committee on Cancer (AJCC) Cancer Staging Manual Eighth Edition Performance status of 0 or 1 on Eastern Cooperative Oncology Group scale (ECOG) American Society of Anesthesiology score (ASA) class I, II, or III Written informed consent Exclusion Criteria: Women during pregnancy or breast-feeding Severe mental disorder History of previous abdominal inflammatory diseases (such as peritonitis, pancreatitis, cholecystitis, inflammatory bowel disease) History of unstable angina or myocardial infarction within past six months History of cerebrovascular accident within past six months History of continuous systematic administration of corticosteroids within one month Emergency surgery due to complication (bleeding, obstruction or perforation) caused by gastric cancer Forced expiratory volume in 1 second (FEV1)<50% of predicted values History of allergy to tracer agents of PET/CT History of allergy to contrast agents of CT

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 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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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 18F-FDG PET/CT and 68Ga-FAPI PET/CT scan after abdominal enhanced CT<br>After the patient received abdominal enhanced CT, 18F-FDG PET/CT and 68Ga-FAPI PET/CT were further performed. The interval between 18F-FDG PET/CT and 68Ga-FAPI PET/CT was 2 days to 1 week. | Diagnostic Test: 68Ga-FAPI PET/CT scan<br>* Each subject receives a single intravenous injection of 68Ga-FAPI, and undergo PET/CT imaging after 18F-FDG PET/CT scan during 2 days and 1 week.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diagnostic efficacy for peritoneal carcinomatosis | Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of 68Ga-FAPI PET/CT for peritoneal carcinomatosis in comparison with 18F-FDG PET/CT and abdominal enhanced CT | One month after surgery | 
| Maximum standardized uptake value [SUVmax (for PET/CT only)] for peritoneal carcinomatosis | SUVmax of 68Ga-FAPI PET/CT for peritoneal carcinomatosis in comparison with 18F-FDG PET/CT | One month after surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Predictive value for peritoneal carcinomatosis by using radiomic algorithm | Prediction value of three kinds of imaging examination for peritoneal carcinomatosis by using radiomic algorithm | One month after surgery | 
| Diagnostic efficacy for primary lesions | Sensitivity, specificity, accuracy, PPV and NPV of 68Ga-FAPI PET/CT for primary lesions in comparison with 18F-FDG PET/CT and abdominal enhanced CT | One month after surgery | 
| SUVmax (for PET/CT only) for primary lesions | SUVmax of 68Ga-FAPI PET/CT for primary lesions in comparison with 18F-FDG PET/CT | One month after surgery | 
| Diagnostic efficacy for metastatic lymph nodes | Sensitivity, specificity, accuracy, PPV and NPV of 68Ga-FAPI PET/CT for metastatic lymph nodes in comparison with 18F-FDG PET/CT and abdominal enhanced CT | One month after surgery | 
| SUVmax (for PET/CT only) for metastatic lymph nodes | SUVmax of 68Ga-FAPI PET/CT for metastatic lymph nodes in comparison with 18F-FDG PET/CT | One month after surgery | 
| Correlation between the expression of fibroblast activation protein (FAP) and 68Ga-FAPI uptake in different pathological types of peritoneal carcinomatosis | Analyzing the correlation between the SUVmax of 68Ga-FAPI in peritoneal carcinomatosis with different pathological types and FAP identified by pathological examinations | One month after surgery | 
| Correlation between the expression of FAP and 68Ga-FAPI uptake in different pathological types of primary lesions | Analyzing the correlation between the SUVmax of 68Ga-FAPI in primary lesions with different pathological types and FAP identified by pathological examinations | One month after surgery | 
| Correlation between the expression of FAP and 68Ga-FAPI uptake in different pathological types of metastatic lymph nodes | Analyzing the correlation between the SUVmax of 68Ga-FAPI in metastatic lymph nodes with different pathological types and FAP identified by pathological examinations | One month after surgery | 
| Predictive value of conversion therapy efficacy | Predictive value of three kinds of imaging examination for gastric cancer in conversion therapy response assessment | One month after surgery | 
| 1-year progression-free survival rate | The relationship between three kinds of imaging examination and the patient's 1-year progression-free survival rate | 12 months | 
| 1-year progression patterns | The relationship between the three types of imaging examinations and the patient's 1-year progression patterns | 12 months |