Objective:The high expression of prostate-specific membrane antigen (PSMA) associated with neovascularization in non-prostatic malignant tumors and metastatic lesions has been documented in many studies. By taking advantage of the absence of PSMA-related background activity in brain tissue, in recent years, PSMA has been used for the imaging of glial tumors, especially for postoperative follow-up. The aim of this prospective study was to investigate the diagnostic value of68Ga-PSMA-11 PET/CT by comparing68Ga-PSMA-11 PET/CT,18F-FDG PET/CT, and MRI findings in patients with brain metastases (BM).Materials and Method:In this prospective study, 27 cases, 11 female and 16 male, with a mean age of 59.48 ± 12.21 years, were included. Patients diagnosed with BM on18F-FDG PET/CT or CT/MRI at initial diagnosis or in the follow-up period were included in the study. PET findings of BM lesions obtained from18F-FDG and68Ga-PSMA-11 PET/CT imaging, demographic characteristics, histopathological data of the primary foci, and other clinical features were evaluated together.Results:Twenty-four (89%) patients were included in the study for restaging, two (7%) patients for local recurrence assessment, and one (4%) patient for local recurrence and suspicion of additional lesions. The indications for18F-FDG PET/CT were breast carcinoma for 37% (n:10), followed by lung carcinoma for 26% (n:7), colorectal adenocarcinoma for 14% (n:4), squamous cell larynx carcinoma for 7% (n:2), gastric signet ring cell carcinoma for 4% (n:1), pancreatic NET3 for 4% (n:1), thyroid papillary carcinoma for 4% (n:1), and malignant melanoma for 4% (n:1). In total, 26/27 included patients had PSMA-positive brain metastases but only one patient had PSMA-negative brain metastases with68Ga-PSMA-11 PET/CT imaging. This patient was followed with a diagnosis of primary larynx squamous carcinoma and had a mass suspected of brain metastases. Further tests and an MRI revealed that the lesion in this patient was a hemorrhagic metastasis. The smallest metastatic focus on68Ga-PSMA-11 PET/CT imaging was 0.22 cm, also confirmed by MRI (range: 0.22–2.81 cm). The mean ± SD SUVmax of the BM lesions was 17.9 ± 8.6 and 6.8 ± 5.2 on18F-FDG PET/CT and68Ga-PSMA-11 PET/CT imaging, respectively. Metastatic foci that could not be detected by18F-FDG PET/CT imaging were successfully detected with68Ga-PSMA-11 PET/CT imaging in 11 cases (42%). The distribution and number of metastatic lesions observed on cranial MRI and68Ga-PSMA-11 PET/CT were compatible with each other for all patients. Immunohistochemical staining was performed in the primary tumor of 10 (38%) cases, and positive IHC staining with PSMA was detected in 5 patients. In addition, positive IHC staining with PSMA was detected in all of the four surgically excised brain metastatic tumor foci.Conclusions:In this study,68Ga-PSMA-11 PET/CT appears to be superior to18F-FDG in detecting BM from various tumors, largely due to its high expression associated with neovascularization and the absence of PSMA expression in normal brain parenchyma. This lack of physiological uptake in healthy brain tissue provides excellent tumor-to-background contrast, further supporting the advantage of68Ga-PSMA-11 over18F-FDG for BM imaging. However, larger studies are required to confirm these findings, particularly through comparisons across tumor types and histopathological subgroups, integrating PSMA immunohistochemistry (IHC) scores with68Ga-PSMA-11 uptake levels. Beyond its diagnostic potential, our results may also inform PSMA-targeted therapeutic strategies, offering new perspectives for the management of patients with brain metastases from diverse primary tumors.
目的：多项研究已证实，非前列腺恶性肿瘤及转移灶中与新生血管相关的前列腺特异性膜抗原（PSMA）高表达现象。近年来，利用脑组织中缺乏PSMA相关背景活性的特点，PSMA已被用于胶质瘤的影像学评估，尤其在术后随访中。本研究旨在通过比较68Ga-PSMA-11 PET/CT、18F-FDG PET/CT及MRI在脑转移瘤（BM）患者中的表现，探讨68Ga-PSMA-11 PET/CT的诊断价值。 材料与方法：这项前瞻性研究共纳入27例患者（女性11例，男性16例），平均年龄59.48±12.21岁。入组标准为初诊或随访期间经18F-FDG PET/CT或CT/MRI确诊为BM的患者。研究综合评估了18F-FDG与68Ga-PSMA-11 PET/CT对BM病灶的显像结果、人口学特征、原发灶组织病理学数据及其他临床特征。 结果：24例（89%）患者因再分期入组，2例（7%）因局部复发评估入组，1例（4%）因局部复发伴可疑新增病灶入组。18F-FDG PET/CT的适应证分布为：乳腺癌37%（10例）、肺癌26%（7例）、结直肠腺癌14%（4例）、喉鳞状细胞癌7%（2例）、胃印戒细胞癌4%（1例）、胰腺NET3 4%（1例）、甲状腺乳头状癌4%（1例）及恶性黑色素瘤4%（1例）。在68Ga-PSMA-11 PET/CT显像中，26/27例（96%）患者呈现PSMA阳性脑转移，仅1例为PSMA阴性脑转移（该患者原发诊断为喉鳞癌，存在疑似脑转移病灶，经进一步检查及MRI证实为出血性转移灶）。68Ga-PSMA-11 PET/CT检测到的最小转移灶直径为0.22 cm（范围0.22–2.81 cm），该结果经MRI确认。BM病灶在18F-FDG PET/CT与68Ga-PSMA-11 PET/CT上的平均SUVmax±标准差分别为17.9±8.6和6.8±5.2。11例（42%）患者中，68Ga-PSMA-11 PET/CT成功检测到18F-FDG PET/CT未能显示的转移灶。所有患者的头颅MRI与68Ga-PSMA-11 PET/CT所观察到的转移灶分布和数量均具有一致性。对10例（38%）患者的原发肿瘤进行免疫组化染色，其中5例显示PSMA阳性；而在4例手术切除的脑转移瘤标本中，所有病灶均检测到PSMA阳性表达。 结论：本研究表明，68Ga-PSMA-11 PET/CT在检测多种肿瘤来源的脑转移方面优于18F-FDG，这主要归因于其与新生血管相关的高表达特性以及正常脑实质中PSMA表达的缺失。健康脑组织缺乏生理性摄取的特点提供了优异的肿瘤-背景对比度，进一步强化了68Ga-PSMA-11相对于18F-FDG在脑转移成像中的优势。然而，仍需更大规模的研究验证这些发现，特别是通过跨肿瘤类型和组织病理学亚组的比较，并将PSMA免疫组化评分与68Ga-PSMA-11摄取水平相结合。除诊断潜力外，本研究结果还可能为PSMA靶向治疗策略提供依据，为不同原发肿瘤来源的脑转移患者管理提供新视角。
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