Impact of 68Ga-FAPI PET/CT on Staging and Oncologic Management in a Cohort of 226 Patients with Various Cancers

Abstract

Since the development of fibroblast activation protein-targeted radiopharmaceuticals, ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI) PET/CT has been found to be suitable for detecting primary and metastatic lesions in many types of tumors. However, there is currently a lack of reliable data regarding the clinical impact of this family of probes. To address this gap, the present study aimed to analyze the clinical impact of ⁶⁸Ga-FAPI PET/CT by examining a large cohort of patients with various tumors. Methods: In total, 226 patients (137 male and 89 female) were included in this retrospective analysis. Pancreatic cancer and head and neck cancers were the most common tumor types in this cohort. TNM stage and oncologic management were initially determined with gold standard imaging, and these results were compared with ⁶⁸Ga-FAPI PET/CT. Changes were classified as major and minor. Results: For 42% of all patients, TNM stage was changed by ⁶⁸Ga-FAPI PET/CT results. Most of these changes resulted in upstaging. A change in clinical management occurred in 117 of 226 patients. Although a major change in management occurred in only 12% of patients, there was a significant improvement in the ability to accurately plan radiation therapy. In general, the highest clinical impact of ⁶⁸Ga-FAPI PET/CT imaging was found in patients with lung cancer, pancreatic cancer, and head and neck tumors. Conclusion: ⁶⁸Ga-FAPI PET/CT is a promising imaging probe that has a significant impact on TNM stage and clinical management. ⁶⁸Ga-FAPI PET/CT promises to be a crucial new technology that will improve on conventional radiologic imaging methods such as contrast-enhanced CT and contrast-enhanced MRI typically acquired for cancer staging.

Keywords: FAPI; PET/CT; management; radiation therapy; staging.

Graphical abstract

FIGURE 1.

Flowchart displaying distribution of exclusion criteria among 449 cancer patients who underwent ⁶⁸Ga-FAPI PET/CT at University Hospital Heidelberg between June 2017 and February 2022 (left side) and fractions of included patients who could be analyzed with regard to TNM staging and clinical management.

FIGURE 2.

Sankey plots displaying ⁶⁸Ga-FAPI PET/CT–related changes in N and M staging of pancreatic cancer (A), head and neck tumors (B), and lung cancer (C). Gray boxes indicate identical staging based on GSI and ⁶⁸Ga-FAPI PET/CT. Red curves indicate upstaging based on ⁶⁸Ga-FAPI PET/CT compared with GSI. Green curves indicate downstaging based on ⁶⁸Ga-FAPI PET/CT compared with GSI.

FIGURE 3.

Relative distribution of ⁶⁸Ga-FAPI PET–related changes in TNM staging (A) and clinical management (B) in different clinical settings (primary staging, follow-up, and progressive disease [PD]/recurrence). Bars are scales to 100% of patients analyzed per group.

FIGURE 4.

Example images of 64-y-old woman with recurrent pancreatic ductal adenocarcinoma. (A) Maximum-intensity projection (MIP) of ⁶⁸Ga-FAPI PET. (B) Axial ⁶⁸Ga-FAPI PET/CT images and contrast-enhanced CT (ceCT) images of suggestive lesions (arrows: lesions 1 and 2, pulmonary metastasis and mediastinal lymph node metastasis; lesion 3, paraaortic lymph node metastasis) detected by ⁶⁸Ga-FAPI PET. HU = Hounsfield units.

FIGURE 5.

Example images of 78-y-old man with primary non–small cell lung cancer. (A) Maximum-intensity projection of ¹⁸F-FDG PET and ⁶⁸Ga-FAPI PET. (B) Axial ¹⁸F-FDG PET/CT and ⁶⁸Ga-FAPI PET/CT of suggestive lesions (arrows: lesion 1, cervical lymph node metastasis; lesion 2, non–small cell lung cancer with involvement of mediastinal lymph nodes; lesion 3, left adrenal mass). Although lesions 1 and 2 were clearly detectable by both PET scans, lesion 3 was ¹⁸F-FDG–avid but not confirmed by ⁶⁸Ga-FAPI PET.