Ora Manish, Saini Vivek Kumar, Dixit Manish, Singh Uday Pratap, Gambhir Sanjay
Department of Nuclear Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
Department of Nuclear Medicine, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India.
Indian J Nucl Med. 2024 May-Jun;39(3):170-176. doi: 10.4103/ijnm.ijnm_8_24. Epub 2024 Aug 17.
Biochemical recurrence (BCR) after initial management of Prostate Carcinoma (PC) is frequent. Subsequent interventions rely on disease burden and metastasis distribution. Ga prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) is an excellent imaging modality in BCR. However, Ga is radionuclide generator produced and has restricted availability. mTc-labeled PSMA could be a potential cost-effective alternative. We compared the performance of Tc-PSMA single-photon emission CT (SPECT)/CT and Ga-PSMA PET/CT in BCR with a serum prostate surface antigen (PSA) level of <20 ng/mL.
The prospective study included 25 patients with BCR and at least one lesion on a Ga-PSMA PET/CT. All patients underwent 99 mTc-PSMA SPECT/CT, and disease distribution and metastatic burden were compared with Ga-PSMA PET/CT. The maximum standard uptake value (SUVmax) and the tumor-to-background ratio (TBR) were computed and analyzed.
The mean age and serum PSA (SPSA) were 69.72 ± 6.69 years and 5.65 ± 6.07 ng/mL. Eleven patients (44%) had SPSA ≤2 ng/mL. Recurrent sites were noted in the prostate (19, 76%), prostatic bed (3, 12%), and pelvis lymph nodes (LNs) (13, 52%). Distant metastasis to bones (13, 52%), lungs (5, 20%), and retroperitoneal LNs (2, 8%) were noted. Both modalities were concordant for the recurrent disease at the prostate, prostatic bed, bone, and lung lesions. Tc-PSMA could localize pelvis LNs in most patients (10/13, 76.9%). The site-specific sensitivity and specificity between the two modalities were not significantly different ( > 0.05). TBR shows excellent correlation with SUVmax (0.783, < 0.001). Four (16%) patients were understaged with Tc-PSMA due to the nonvisualization of the subcentimeter size LNs. No patient with systemic metastases was understaged.
Tc-PSMA SPECT/CT has good concordance with Ga-PSMA PET/CT in BCR, even at low PSA levels. However, it may miss a few subcentimeter LNs due to lower resolution. Tc-PSMA SPECT/CT could be a simple, cost-effective, and readily available imaging alternative to PET/CT.
前列腺癌（PC）初始治疗后生化复发（BCR）很常见。后续干预取决于疾病负担和转移分布。镓前列腺特异性膜抗原正电子发射断层扫描/计算机断层扫描（PSMA PET/CT）是BCR中一种出色的成像方式。然而，镓是通过放射性核素发生器产生的，可用性有限。锝标记的PSMA可能是一种潜在的具有成本效益的替代方案。我们比较了血清前列腺特异性抗原（PSA）水平<20 ng/mL的BCR患者中锝-PSMA单光子发射计算机断层扫描（SPECT）/CT和镓-PSMA PET/CT的性能。
前瞻性研究纳入了25例BCR患者，且在镓-PSMA PET/CT上至少有一个病灶。所有患者均接受了99m锝-PSMA SPECT/CT检查，并将疾病分布和转移负担与镓-PSMA PET/CT进行比较。计算并分析了最大标准摄取值（SUVmax）和肿瘤与本底比值（TBR）。
患者的平均年龄和血清PSA（SPSA）分别为69.72±6.69岁和5.65±6.07 ng/mL。11例患者（44%）的SPSA≤2 ng/mL。复发部位见于前列腺（19例，76%）、前列腺床（3例，12%）和盆腔淋巴结（LNs）（13例，52%）。还发现有远处转移至骨（13例，52%）、肺（5例，20%）和腹膜后LNs（2例，8%）。两种检查方式在前列腺、前列腺床、骨和肺部病变的复发疾病方面具有一致性。锝-PSMA在大多数患者（10/13，76.9%）中能够定位盆腔LNs。两种检查方式在部位特异性的敏感性和特异性方面无显著差异（P>0.05）。TBR与SUVmax显示出良好的相关性（0.783，P<0.001）。4例（16%）患者因未发现亚厘米大小的LNs而被锝-PSMA低估分期。没有全身转移的患者被低估分期。
在BCR中，即使在低PSA水平下，锝-PSMA SPECT/CT与镓-PSMA PET/CT也具有良好的一致性。然而，由于分辨率较低，它可能会遗漏一些亚厘米大小的LNs。锝-PSMA SPECT/CT可能是一种简单、具有成本效益且易于获得的PET/CT成像替代方案。
