PurposeThe 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.MaterialsIn 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.

A left pulmonary nodule was identified by CT scan in a 53-year-old woman who had a car accident 10 days earlier. 18F-FDG PET/CT showed multiple FDG-avid lesions located at the left lung nodule, mediastinal lymph nodules, and L4 vertebral body. 68Ga-FAPI PET/CT was performed for further evaluation. However, 68Ga-FAPI demonstrated intense FAPI uptake in the accident-related fracture of the L4 vertebral body. This case documents that the fracture of the vertebral body may cause FAPI uptake, and nuclear clinicians evaluating 68Ga-FAPI imaging should be aware of this potential pitfall.

ObjectiveTo conduct a meta-analysis of the efficacy and safety of 225Ac-PSMA-617 in the treatment of metastatic castration-resistant prostate cancer based on existing clinical evidence.MethodsSearch for retrospective studies about 225Ac-PSMA-617 in the treatment of metastatic castration-resistant prostate cancer from establishment to July 2021 in PubMed and EMBASE. The primary endpoint was 225Ac-PSMA-617 biochemical response evaluation criteria after treatment [any prostate specific antigen (PSA) decrease and PSA decrease >50% from baseline] to evaluate the treatment effect. Secondary endpoints included assessment of overall survival (OS), progression-free survival (PFS), molecular response, and toxicity for all studies. Two researchers conducted literature screening, data extraction and quality evaluation according to the inclusion and exclusion criteria. Use stata16.0 software for analysis, fixed-effects model for data merging and forest plots for display.ResultsA total of 6 retrospective studies, namely, 201 patients, were included in the final analysis. The pooled proportions of patients with decreased PSA and PSA decreased by more than 50% were 87.0% (95% confidence interval, 0.820 to 0.920) and 66.1% (95% confidence interval, 0.596 to 0.726), respectively. The pooled proportions of OS and PFS were 12.5 months (95%CI: 6.2–18.8 months) and 9.1 months (95%CI: 2.6–15.7 months). The patients showing molecular responses were 54% (95% confidence interval: 25–84%). In all studies, the most common side effect of 225Ac-PSMA-617 TAT was xerostomia, with any degree of xerostomia occurring in 77.1% (155 out of 201), and grade III only accounted for 3.0%. The second was 30.3% (61 out of 201) anemia of any degree, and grade III accounts for 7.5% (15 out of 201). Grade III leukopenia and thrombocytopenia were 4.5% (9 out of 201) and 5.5% (11 out of 201), respectively. Only 6 (3.0%) of 201 patients had Grade III nephrotoxicity.Conclusion225Ac-PSMA-617 is an effective and safe treatment option for mCRPC patients, and the toxicity caused by it is relatively low. However, future randomized controlled trials and prospective trials are required in the future to judge the therapeutic effects and survival benefits compared with existing clinical treatments.Systematic Review RegistrationPROSPERO: CRD42021281967.