In up to two thirds of prostate-specific membrane antigen (PSMA) PET scans, unspecific bone uptake has been described. The aim of this study was to estimate the diagnostic accuracy of [⁶⁸Ga]Ga-PSMA-11 PET/CT for bone metastases and the occurrence of equivocal lesions. Methods: We analyzed retrospectively 118 patients who underwent a [⁶⁸Ga]Ga-PSMA-11 PET/CT for initial staging or recurrence evaluation. Lesions were interpreted according to the PSMA reporting and data system (PSMA-RADS) and the prostate cancer molecular imaging standardized evaluation (PROMISE) criteria. The SUV_max and the localization of each lesion were recorded. A combination of prior or follow-up examinations was used as a reference standard to categorize benign and malignant lesions. Correlation between the final diagnosis and imaging or clinicobiochemical parameters was tested. The diagnostic accuracy was calculated for different cutoffs of PSMA-RADS criteria, for PROMISE criteria, and the sequential combination of both. Results: In total, 265 bone abnormalities were identified in 70 of 118 patients. Among these, 148 (55.8%) lesions in 50 (42.4%) patients were classified as PSMA-RADS-3B. There were no PSMA-RADS-3D lesions in our cohort. Equivocal lesions were more frequent on the ribs (30.6%) followed by the pelvis (26.5%), but in the ribs, such an uptake was malignant in 33.3% of cases versus 66.7% in the pelvis. A significant association was found between the final diagnosis and the SUV_max, prostate-specific antigen (PSA), PSA doubling time, International Society of Urological Pathology score, and the number of foci. The sensitivity and specificity were 100% and 63.6% for the PSMA-RADS-3B cutoff, respectively; 40.5% and 100% for the PSMA-RADS-4 cutoff, respectively; and 89.3% and 96.6% for both the PROMISE criteria and the sequential PSMA-RADS/PROMISE strategy, respectively. In the sequential method, the number of equivocal lesions was reduced from 147 to 2. We found that 53% of PSMA-RADS-3B lesions were malignant; 95.5% of lesions classified positive by the sequential method were true positives, whereas 32.6% were false negatives. Conclusion: [⁶⁸Ga]Ga-PSMA-11 PET/CT has high accuracy for the diagnosis of bone metastases. Equivocal lesions constitute nearly half of the lesions seen on PSMA PET. The sequential combination of PSMA-RADS and PROMISE criteria reduces the number of lesions classified as equivocal. PSMA-RADS-3B lesions which are positive according to the PROMISE criteria should be considered highly suggestive of malignancy.

在多达三分之二的前列腺特异性膜抗原 (PSMA) PET 扫描中，描述了非特异性骨摄取。本研究的目的是评估[ ⁶⁸ Ga]Ga-PSMA-11 PET/CT 对骨转移和可疑病变发生的诊断准确性。方法：我们回顾性分析了 118 名接受 [ ⁶⁸ Ga]Ga-PSMA-11 PET/CT 进行初始分期或复发评估的患者。根据 PSMA 报告和数据系统 (PSMA-RADS) 和前列腺癌分子成像标准化评估 (PROMISE) 标准对病变进行解释。记录 SUV _max和每个病变的定位。结合先前或随访检查作为良性和恶性病变分类的参考标准。测试了最终诊断与影像学或临床生化参数之间的相关性。根据 PSMA-RADS 标准、PROMISE 标准以及两者的顺序组合的不同截止值计算诊断准确性。结果： 118 名患者中有 70 名总共发现了 265 处骨异常。其中，50 名 (42.4%) 患者的 148 个 (55.8%) 病变被分类为 PSMA-RADS-3B。我们的队列中没有 PSMA-RADS-3D 病变。肋骨（30.6%）的可疑病变更为常见，其次是骨盆（26.5%），但在肋骨中，这种摄取为恶性的病例为 33.3%，而骨盆为 66.7%。最终诊断与 SUV _max 、前列腺特异性抗原 (PSA)、PSA 倍增时间、国际泌尿病理学会评分和病灶数量之间存在显着相关性。敏感性和特异性分别为 100% 和 63。PSMA-RADS-3B 截止值分别为 6%； PSMA-RADS-4 截止值分别为 40.5% 和 100%； PROMISE 标准和顺序 PSMA-RADS/PROMISE 策略分别为 89.3% 和 96.6%。在序贯法中，可疑病变的数量从 147 个减少到 2 个。我们发现 53% 的 PSMA-RADS-3B 病变是恶性的；序贯法分类为阳性的病变中，95.5% 为真阳性，32.6% 为假阴性。结论： [ ⁶⁸ Ga]Ga-PSMA-11 PET/CT对骨转移的诊断准确率较高。可疑病变占 PSMA PET 所见病变的近一半。 PSMA-RADS 和 PROMISE 标准的顺序组合减少了被分类为模棱两可的病变数量。根据 PROMISE 标准呈阳性的 PSMA-RADS-3B 病变应被视为高度提示恶性肿瘤。