Dual targeting PET tracer [⁶⁸Ga]Ga-FAPI-RGD in patients with lung neoplasms: a pilot exploratory study

Rationale: Early discovery, accurate diagnosis, and staging of lung cancer is essential for patients to receive appropriate treatment. PET/CT has become increasingly recognized as a valuable imaging modality for these patients, but there remains room for improvement in PET tracers. We aimed to evaluate the feasibility of using [Ga-68]Ga-FAPI-RGD, a dual-targeting heterodimeric PET tracer that recognizes both fibroblast activation protein (FAP) and integrin alpha(v)beta(3) for detecting lung neoplasms, by comparing it with [F-18]FDG and single-targeting tracers [Ga-68]Ga-RGD and [Ga-68]Ga-FAPI. Methods: This was a pilot exploratory study of patients with suspected lung malignancies. All 51 participants underwent [Ga-68]Ga-FAPI-RGD PET/CT, of which: 9 participants received dynamic scans, 44 participants also underwent [F-18]FDG PET/CT scan within two weeks, 9 participants underwent [Ga-68]Ga-FAPI PET/CT scan and 10 participants underwent [Ga-68]Ga-RGD PET/CT scan. The final diagnosis was made based on histopathological analyses and clinical follow-up reports. Results: Among those who underwent dynamic scans, the uptake of pulmonary lesions increased over time. The optimal timepoint for a PET/CT scan was identified to be 2 h post-injection. [Ga-68]Ga-FAPI-RGD had a higher detection rate of primary lesions than [F-18]FDG (91.4% vs. 77.1%, p < 0.05), higher tumor uptake (SUVmax, 6.9 +/- 5.3 vs. 5.3 +/- 5.4, p < 0.001) and higher tumor-to-background ratio (10.0 +/- 8.4 vs. 9.0 +/- 9.1, p < 0.05), demonstrated better accuracy in mediastinal lymph node evaluation (99.7% vs. 90.9%, p < 0.001), and identified more metastases (254 vs. 220). There was also a significant difference between the uptake of [Ga-68]Ga-FAPI-RGD and [Ga-68]Ga-RGD of primary lesions (SUVmax, 5.8 +/- 4.4 vs. 2.3 +/- 1.3, p < 0.001). Conclusion: In our small scale cohort study, [Ga-68]Ga-FAPI-RGD PET/CT gave a higher primary tumor detection rate, higher tracer uptake, and improved detection of metastases compared with [F-18]FDG PET/CT, and [Ga-68]Ga-FAPI-RGD also had advantages over [Ga-68]Ga-RGD and was non-inferior to [Ga-68]Ga-FAPI. We thus provide proof-of-concept for using [Ga-68]Ga-FAPI-RGD PET/CT for diagnosing lung cancer. With the stated advantages, the dual-targeting FAPI-RGD should also be explored for therapeutic use in future studies.