The Role of 18F-FDG and 68Ga-FAPI PET/CT in the Diagnosis and the Efficacy Evaluation of Advanced Colorectal Cancer (peritoneal Metastasis With/without Other Metastases)

This study is evaluating two types of PET/CT scans — one using a standard tracer (18F-FDG) and one using a newer tracer (68Ga-FAPI) that targets cancer-associated tissue — to improve the diagnosis and monitoring of colorectal cancer that has spread to the lining of the abdomen (peritoneal metastasis). **You may be eligible if...** - You have been confirmed by biopsy to have colorectal cancer - Imaging or clinical findings suggest your cancer may have spread to the lining of the abdomen, with or without other distant spread - You are 18 or older - Your life expectancy is at least 3 months - Your organ and bone marrow function is adequate **You may NOT be eligible if...** - You are pregnant or breastfeeding - You have had another type of cancer in the past 5 years (except cured skin cancer or cervical carcinoma in situ) - You have severe mental illness, uncontrolled epilepsy, or a central nervous system condition - You have or have had significant lung conditions such as interstitial pneumonitis, pulmonary fibrosis, or active tuberculosis Talk to your doctor to see if this trial is right for you.