18F-FDG PET/CT Identified Rectal Malignancy Earlier Than 68Ga-FAPI PET/CT

A 69-year-old man with esophageal cancer underwent dual-tracer PET/CT using 18F-FDG and 68Ga-FAPI during his treatment. At baseline, neither scan showed abnormal uptake in the rectum. Three months later, an interim 18F-FDG PET/CT revealed focal uptake in the rectum, while the 68Ga-FAPI PET/CT showed no abnormal findings. Seventeen months later, he received a third dual-tracer PET/CT for surveillance. Both 18F-FDG and 68Ga-FAPI PET/CT detected abnormal activity in the same area of the rectum​​​​​​. The lesion was later confirmed as adenocarcinoma by histopathology after surgery. Our case demonstrated the 18F-FDG PET/CT could identify the rectal malignancy before 68Ga-FAPI PET/CT.