Clinical Value of Dual Tracer PET Imaging With 68Ga-PSMA and 18F-FDG in Patients With Metastatic Prostate Cancer
Objective In this study,we retrospectively analyzed the imaging characteristics of dual-tracer 68Ga-prostate specific membrane antigen(PSMA)and 18F-flurodeoxyglucose(FDG)positron emission tomography(PET)/computed tomography(CT)in metastatic prostate cancer(mPCa)patients.We analyzed the uptake modes of the dual tracers,explored clinical pathological parameters affecting the 18F-FDG uptake in the lesions,and evaluated their prognostic implications for prostate specific antigen progression-free survival(PSA-PFS).Methods A total of 41 mPCa patients who underwent dual-tracer PET/CT(68Ga-PSMA and 18F-FDG)scans between September 2021 and January 2024 were retrospectively enrolled.One patient had negative uptake of both PSMA and FDG.According to the uptake patterns of the 2 tracers,the other patients,40 in total,were categorized in 2 groups,including group A consisting of 33 cases who showed PSMA and FDG dual and those who showed FDG only avidity,and group B consisting of 7 cases who showed PSMA avidity only.Comparative analyses of clinical pathological characteristics between group A and group B were conducted.The relationship between various parameters and PSA-PFS was analyzed by the Kaplan-Meier method.Results A total of 26 patients(63.4％)were diagnosed with metastatic castration-resistant prostate cancer(mCRPC),and 38 cases(92.7％)had a Gleason score of 8-9.Bone metastasis,the predominant type of distant metastasis,occurred in 36 cases(87.8％).The skeletal and distant lymph node metastases mostly showed a dual positive uptake pattern for both PSMA and FDG(85.7％[24/28]and 81.8％[9/11]).37.5％(3/8)of the metastases to organs showed FDG only positive uptake pattern.The serum levels of prostate specific antigen(PSA)in group A were significantly higher than those in group B(P=0.013).A total of 13 patients of special pathological classification(intraductal carcinoma and neuroendocrine differentiation)were all found to be in group A.Among the 41 cases,16 were lost to follow-up.Of the 25 patients who completed follow-up,9 patients,with a median PSA value of 104 ng/mL,experienced PSA progression,while the 16 other patients,with a median PSA of 0.34 ng/mL,did not incur any PSA progression.There was significant difference in the median PSA between patients showing PSA progression and those who did not show PSA progression(P＜0.001).Kaplan-Meier survival analysis revealed that the median PSA-PFS of patients of specific pathological classifications was 7 months,which was shorter than the 16 months of the patients with typical prostate cancer,with the difference between the two groups being statistically meaningful(P=0.043).The median PSA-PFS for group A was 30 months.With more than half of the patients in the group not experiencing any PSA progression,group B did not reach the median PSA-PFS(P=0.645).Conclusion Dual-tracer PET/CT imaging with 68Ga-PSMA and 18F-FDG commonly exhibits avidity for both tracers in mPCa.Serum PSA level is a reliable biomarker for predicting FDG-positive lesions.mPCa presented with intraductal carcinoma and neuroendocrine differentiation tends to exhibit FDG avidity and is more susceptible to PSA progression.
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