Comparison of the Relative Diagnostic Performance of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT for the Detection of Bone Metastasis in Patients With Different Cancers

Abstract

Purpose: The present retrospective analysis sought to compare the relative diagnostic efficacy of [⁶⁸Ga]Ga-DOTA-FAPI-04 to that of [¹⁸F]FDG PET/CT as a means of detecting bone metastases in patients with a range of cancer types.

Materials: In total, 30 patients with bone metastases associated with different underlying malignancies were retrospectively enrolled. All patients had undergone [⁶⁸Ga]Ga-DOTA-FAPI-04 and [¹⁸F]FDG PET/CT, and the McNemar test was used to compare the relative diagnostic performance of these two imaging modalities. The maximum standard uptake value (SUVmax) was used to quantify radiotracer uptake by metastatic lesions, with the relative uptake associated with these two imaging strategies being compared via the Mann-Whitney U test. The cohort was further respectively divided into two (osteolytic and osteoblastic bone metastases) and three clinical subgroups (lung cancer, thyroid cancer, and liver cancer).

Results: [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT was found to be significantly more sensitive as a means of diagnosing bone metastases relative to [¹⁸F]FDG PET/CT ([109/109] 100% vs [89/109] 81.7%; P< 0.01), consistent with the significantly increased uptake of [⁶⁸Ga]Ga-DOTA-FAPI-04 by these metastatic lesions relative to that of [¹⁸F]FDG (n=109, median SUVmax, 9.1 vs. 4.5; P< 0.01). [⁶⁸Ga]Ga-DOTA-FAPI-04 accumulation was significantly higher than that of [¹⁸F]FDG in both osteolytic (n=66, median SUVmax, 10.6 vs 6.1; P < 0.01), and osteoblastic metastases (n=43, median SUVmax, 7.7 vs 3.7; P < 0.01). [⁶⁸Ga]Ga-DOTA-FAPI-04 uptakes were significantly higher than that of [¹⁸F]FDG in bone metastases from lung cancer (n = 62, median SUVmax, 10.7 vs 5.2; P < 0.01), thyroid cancer (n = 18, median SUVmax, 5.65 vs 2.1; P < 0.01) and liver cancer (n = 12, median SUVmax, 5.65 vs 3.05; P < 0.01). However, [⁶⁸Ga]Ga-DOTA-FAPI-04 detected 10 false-positive lesions, while only 5 false-positive were visualized by [¹⁸F]FDG PET/CT.

Conclusion: [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT exhibits excellent diagnostic performance as a means of detecting bone metastases, and is superior to [¹⁸F]FDG PET/CT in this diagnostic context. Furthermore, [⁶⁸Ga]Ga-DOTA-FAPI-04 tracer uptake levels are higher than those of [¹⁸F]FDG for most bone metastases. However, owing to the potential for false-positive bone lesions, it is critical that physicians interpret all CT findings with caution to ensure diagnostic accuracy.

Keywords: PET/CT; [18F]FDG; [68Ga]Ga-DOTA-FAPI-04; bone metastases; cancer.

Figure 1

The SUVmax of FAPI and FDG in 77 bone metastatic lesions. The tracer accumulation of [⁶⁸Ga]Ga-FAPI-04 in bone metastases is significantly higher than that of [¹⁸F]FDG (n=109, median SUVmax, 9.1 vs 4.5; P< 0.01, respectively).

Figure 2

The SUVmax of FAPI and FDG in osteolytic and osteoblastic lesions. [⁶⁸Ga]Ga-DOTA-FAPI-04 accumulation was significantly higher than that of [¹⁸F]FDG in both osteolytic (n=66, median SUVmax, 10.6 vs 6.1; P < 0.01), and osteoblastic metastases (n=43, median SUVmax, 7.7 vs 3.7; P < 0.01).

Figure 3

A 46-year-old woman with a newly diagnosed lung cancer underwent [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT (A, B). The MIP images (A, B) of the [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT showed multiple bone lesions. On the selected axial images, [¹⁸F]FDG PET/CT (A) only showed mild to moderate [¹⁸F]FDG activities on thoracic vertebrae (arrows) and right acetabulum (dashed arrows), whereas [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT (B) showed intense [⁶⁸Ga]Ga-DOTA-FAPI-04 uptakes in thoracic vertebrae (arrows) and right acetabulum (dashed arrows).

Figure 4

A 63-year-old man was received [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT (A, B) to evaluate the new diagnosed lung cancer. The MIP image (A, B) of [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT demonstrated multiple bone lesions. On the selected axial images, [¹⁸F]FDG PET/CT (A) only showed slight [¹⁸F]FDG activities in the clivus (arrows) and lumbar vertebral (dashed arrows). On the contrary, intense FAPI uptakes in the clivus (arrows) and lumbar vertebral (dashed arrows) were obviously observed on [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT.

Figure 5

The SUVmax of FAPI and FDG in bone metastases from lung cancer, thyroid cancer and liver cancer. [⁶⁸Ga]Ga-DOTA-FAPI-04 accumulation was significantly higher than that of [¹⁸F]FDG in bone metastases from lung cancer (n = 62, median SUVmax, 10.7 vs 5.2; P < 0.01), thyroid cancer (n = 18, median SUVmax, 5.65 vs 2.1; P < 0.01) and liver cancer (n = 12, median SUVmax, 5.65 vs 3.05; P < 0.01).

Figure 6

Characteristic findings of Schmorl Node (A) and degenerative osteophyte (B). The Schmorl Node in the patient with lung cancer (A) shows tracer uptake on the [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT, while no uptake on the [¹⁸F]FDG PET/CT. The degenerative osteophyte in the patient with lung cancer (B) shows tracer accumulation on [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT.

Figure 7

A 76-year-old woman underwent [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT (A, B) to assess possible recurrence of thyroid cancer. The MIP image (A, B) of [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT demonstrated multiple tracer activities bone and liver lesions. On the selected axial images, [¹⁸F]FDG PET/CT (A) showed limited [¹⁸F]FDG uptakes in the parietal bone (arrows) and clivus (dashed arrows), while [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT (B) showed intense [⁶⁸Ga]Ga-DOTA-FAPI-04 uptakes in the parietal bone (arrows) and clivus (dashed arrows). In addition, the expression of [⁶⁸Ga]Ga-DOTA-FAPI-04 in liver metastasis was significantly higher than that of [¹⁸F]FDG.