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.
目的: 本研究回顾性收集进行68镓（68Ga）-前列腺特异性膜抗原（prostate specific membrane antigen, PSMA）和18氟（18F）-代脱氧葡萄糖（flurodeoxyglucose, FDG）正电子发射计算机断层成像（PET/CT）显像的转移性前列腺癌（metastatic PCa, mPCa），分析双示踪剂摄取模式，影响病灶摄取18F-FDG的临床病理学参数及影响前列腺特异性抗原（prostate specific antigen, PSA）-无进展生存期（progression-free survival, PFS）的预后分析。
方法: 回顾性纳入2021年9月–2024年1月间于我院行68Ga-PSMA 及18F-FDG PET/CT双示踪剂显像的41例mPCa。除外1例PSMA、FDG双阴性摄取，基于是否存在FDG阳性病灶，将剩余40例分为两组：Group A（PSMA、FDG双阳性组和FDG单阳性组，33例）；Group B（PSMA单阳性组，7例）。比较Group A和Group B组间临床病理学特点。通过Kaplan-Meier法分析不同参数与PSA-PFS的关系。
结果: 26例（63.4%）患者为转移性去势抵抗性PCa（metastatic castration-resistant PCa, mCRPC），Gleason 评分 8～9 分38例（92.7%），远处转移以骨骼转移（36例，87.8%）为主。骨骼及远处淋巴结转移灶多表现为PSMA、FDG双阳性摄取模式〔85.7%（24/28），81.8%（9/11）〕；在脏器转移灶中，37.5%（3/8）存在FDG单阳性的摄取模式。Group A血清PSA水平高于Group B（P=0.013）。13例特殊病理类型（导管内癌和神经内分泌分化）患者均在Group A。41例患者中，16例患者失访。25例完成随访的患者中9例患者发生PSA进展，PSA中位值为104 ng/mL；16 例患者无PSA进展，PSA中位值为0.34 ng/mL，两组间PSA中位值差异有统计学意义（P<0.001）。Kaplan-Meier生存分析显示特殊病理类型中位PSA-PFS（7个月） 短于经典型PCa（16个月），两组间差异有统计学意义（P=0.043）；Group A中位PSA-PFS为30个月，Group B仍有超过一半的个体尚未发生PSA进展，中位PSA-PFS尚未达到（P=0.645）。
结论: mPCa多表现为68Ga-PSMA和18F-FDG双示踪剂摄取，血清PSA水平是预测病灶FDG阳性的可靠指标。存在导管内癌及神经内分泌分化的mPCa病灶易表现为FDG阳性且出现PSA进展。
Keywords: 18F-FDG; 68Ga-PSMA; Heterogeneity; Metastatic prostate cancer.
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