Predicting the unpredictable: prognostic and predictive power of FAPI-PET imaging in oncology: a systematic review and meta-analysis.

[OBJECTIVES] In this systematic review, we evaluated the accuracy of baseline fibroblast activation protein inhibitor (FAPI)-based PET scans for predicting overall survival (OS), progression-free survival (PFS), and tumor response after treatment completion.

[METHODS] We searched PubMed and Cochrane Library until August 2025 to identify studies that evaluated the prognostic and predictive value of FAPI-based PET scans parameters in the OS, PFS, and treatment response of cancer patients; all studies reporting these findings, whether as the main or a secondary finding, were included.

[RESULTS] Of the forty-seven publications, including 1430 patients, various cancer types from breast to pancreatic cancer, were evaluated. The pooled hazard ratio (HR) indicated that patients with higher maximum standardized uptake value (SUVmax) were significantly associated with poor OS (HR: 2.36; 95% CI: 1.56-3.56, p < 0.011) and poor PFS (HR: 1.88; 95% CI: 1.36-2.60, p < 0.001). Patients with higher FAPI-avid tumor volume (MTV) were significantly associated with poorer OS (HR: 3.33; 95% CI: 1.99-5.56, p < 0.001) and PFS (HR: 2.42; 95% CI: 1.60-3.67, p < 0.001). High total lesion FAP expression (TLFAPI) was significantly associated with poorer OS (HR: 3.35; 95% CI: 2.05-5.50, p < 0.001) and PFS (HR: 2.45, 95% CI: 1.61-3.73, p < 0.001).

[CONCLUSION] Early evidence indicates that FAPI PET parameters, especially the baseline of MTV, SUVmax, and TLFAPI, can be proper prognostic markers of OS and PFS in cancers by imaging tumor stroma. In various cancers, FAPI uptake parameters change after treatment, or baseline levels are linked to treatment outcomes.