Human papillomavirus (HPV) infection in heterosexual South African men attending sexual health services: associations between HPV and HIV serostatus

625 Objectives: Targeting fibroblast activation protein (FAP) is a new diagnostic approach allowing the visualization of tumor stroma. ⁶⁸Ga-labeled FAP ligands (⁶⁸Ga-FAPI) have been recently developed and were found promising alternatives to ¹⁸F-FDG in cancer patients. In this study, we evaluated the potential usefulness of ⁶⁸Ga-FAPI PET/CT for detection, staging and restaging of various kinds of cancer, and compared with conventional ¹⁸F-FDG PET/CT. Methods: Approved by the Clinical Research Ethics Committee, we prospectively enrolled patients with pathologically confirmed primary tumors or metastases. All patients underwent contemporaneous ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG PET/CT either for initial assessment (detection, staging) or for recurrence detection (restaging). The ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT were conducted within 48 h of each other, and all studies were reviewed by consensus of 2 senior nuclear medicine physicians. Tumor uptake was quantified by SUVmax. Individual lymph nodes; nodal masses; and lung, skeletal, and solid organ lesions were coded as positive if the tracer uptake exceeded that of adjacent background tissues. Results: Sixty-five patients (39 male and 26 female, median age, 61 y, age range, 32-85 y) comprised the study cohort. Forty-two patients with 12 different tumor entities underwent paired ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT for initial tumor detection and staging, and the other 23 patients with 6 different tumor entities underwent PET/CT for detecting recurrence and for restaging purpose. Twelve different tumor entities presented with remarkably high tumor-to-background contrast in ⁶⁸Ga-FAPI PET/CT. Except for one case with hemangiosarcoma, ⁶⁸Ga-FAPI PET demonstrated significantly higher tumor uptake than that of ¹⁸F-FDG PET, especially in colorectal cancer (13.9±4.4 vs. 7.2±6.7), gastric cancer (14.5±6.8vs. 8.2±3.7), pancreatic cancer (26.0±8.5 vs. 3.7±3.4), liver cancer (19.4±6.2 vs. 4.7±5.5) and ovarian cancers (13.8±2.2 vs. 6.7±1.8). More importantly, due to the low background uptake in the brain, liver and abdominal cavity, ⁶⁸Ga-FAPI PET/CT revealed more metastatic lesions than ¹⁸F-FDG PET/CT in the brain, liver, omentum and mesentery. ⁶⁸Ga-FAPI PET/CT also showed more bone metastases in axial skeleton than ¹⁸F-FDG PET/CT.Furthermore, ⁶⁸Ga-FAPI PET/CT revealed more metastatic lymph nodes than ¹⁸F-FDG PET/CT in the neck, supraclavicular and paraaortic regions. Conclusions: ⁶⁸Ga-FAPI PET/CT is useful for detection, staging and restaging of various kinds of cancer. One advantage of ⁶⁸Ga-FAPI PET/CT over conventional ¹⁸F-FDG PET/CT is that it revealed more metastatic lesions in the region of brain, liver, omentum, and mesentery. It also revealed more metastatic lymph nodes in the neck, supraclavicular and paraaortic regions.