PET/CT imaging with a new fibroblast activation protein inhibitor (FAPI) imaging agent detects more bone metastases than FDG-PET/CT in patients with different types of cancer, researchers have reported.
In a retrospective analysis that included 293 patients, gallium-68 (Ga-68) DOTA-FAPI-04 uptake was greater than F-18 FDG uptake by both benign bone lesions and metastases, especially for osteoblastic metastasis, noted lead author Rui Guo, MD, of Peking University Cancer Hospital and Institute in China, and colleagues.
“Because Ga-68 DOTA-FAPI-04 PET/CT can detect bone metastases at an early stage and improve the accuracy of staging, it can provide good guidance for the treatment of tumor patients, thereby improving the survival rate and quality of life of patients,” the group wrote. The study was published March 12 in Bone.
Bone is one of the most common sites of cancer metastasis for various solid tumors outside of the lungs and liver, with up to 80% of these patients eventually developing bone metastases, the authors explained. While F-18 FDG is the most commonly used agent for detecting cancer, its sensitivity is relatively low for detecting bone lesions, they noted.
Hence, the group analyzed whether Ga-68 DOTA-FAPI-04, a new tracer that has shown promise over F-18 FDG for detecting primary tumors, may also be more accurate for detecting bone metastases. They analyzed imaging from 293 patients with pathologically confirmed primary malignancies who had undergone PET/CT scans with both agents within one week between November 2019 and December 2022.
Patients had various types of tumors, including lung cancer, sarcoma, gastrointestinal malignancies, thyroid cancer, breast cancer, and other malignancies, the researchers noted. In total, 48 were diagnosed with bone metastasis, with 376 bone metastases and 243 benign bone lesions ultimately identified.
According to the analysis, based on radiotracer uptake by lesions, Ga-68 DOTA-FAPI-04 PET/CT detected 376 metastatic lesions and 243 benign lesions and F-18 FDG-PET/CT detected 228 metastatic lesions 44 benign.
| Ga-68 DOTA-FAPI-04 vs. F-18 FDG PET/CT for detecting bone metastases | ||
|---|---|---|
| F-18 FDG | Ga-68 DOTA-FAPI-04 | |
| Sensitivity | 61% | 100% |
| Specificity | 99% | 94% |
| Positive predictive value | 99% | 96% |
| Negative predictive value | 62% | 100% |
| Accuracy | 76% | 98% |
“These findings indicate that Ga-68 DOTA-FAPI-04 PET/CT is superior in detecting and staging bone metastases in tumor patients compared to F-18 FDG-PET/CT due to its early detection capability and increased sensitivity,” the group wrote.
However, the researchers added that Ga-68 DOTA-FAPI-04 PET/CT resulted in a higher false positive rate, with 15 cases of false positives, including Fibrous dysplasia, arthritis, and fractures, compared with two false-positives cases with F-18 FDG-PET/CT. This reduces the specificity of the technique, they wrote.
“Further studies with larger sample sizes are needed to further analyze the use range of Ga-68 DOTA-FAPI-04 PET/CT in patients with bone metastasis,” the group concluded.
The full study is available here.