Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
Department of Radiology and Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands.
J Nucl Med. 2023 Oct;64(10):1556-1562. doi: 10.2967/jnumed.123.265489. Epub 2023 Aug 3.
CT and bone scintigraphy are not useful for response evaluation of bone metastases to Ra treatment in metastatic castration-resistant prostate cancer (mCRPC). PET using Ga prostate-specific membrane antigen 11 (Ga-PSMA) is a promising tool for response evaluation of mCRPC. The aim of this study was to determine the utility of Ga-PSMA PET/CT for response evaluation of Ra treatment in patients with mCRPC. Within this prospective, multicenter, imaging discovery study, 28 patients with mCRPC, eligible for Ra treatment, were included between 2019 and 2022. Patients received Ra according to the standard of care. Study procedures included CT, bone scintigraphy, and Ga-PSMA PET/CT at baseline, after 3 and 6 cycles of Ra treatment, and on treatment failure. Response to Ra treatment was visually assessed on all 3 imaging modalities. Total tumor volume within bone (TTV) was determined on Ga-PSMA PET/CT. Intrapatient heterogeneity in response was studied using a newly developed image-registration tool for sequential images of PET/CT. Results were compared with failure-free survival (good responders vs. poor responders; cutoff, 24 wk) and alkaline phosphatase (ALP) response after 3 cycles. Visual response assessment criteria could not distinguish good responders from poor responders on Ga-PSMA PET/CT and bone scintigraphy. For Ga-PSMA PET/CT, TTV at baseline was lower in good responders than in poor responders, whereas TTV increased in both groups during treatment. TTV was higher in patients with new extraosseous metastases during Ra treatment. Although TTV and ALP correlated at baseline, changes in TTV and ALP on treatment did not. Ga-PSMA response of TTV showed intrapatient heterogeneity in most patients. mCRPC patients with lower TTV on Ga-PSMA PET/CT have the best clinical outcome after Ra treatment. Response is highly heterogeneous in most patients. A decrease in ALP, which occurred in most patients, was not correlated with a decrease in TTV, which might make one question the value of ALP for disease monitoring during Ra treatment in clinical practice.
CT 和骨闪烁扫描对于转移性去势抵抗性前列腺癌（mCRPC）患者的镭治疗骨转移的反应评估没有帮助。使用 Ga 前列腺特异性膜抗原 11（Ga-PSMA）的 PET 是评估 mCRPC 反应的一种很有前途的工具。本研究的目的是确定 Ga-PSMA PET/CT 在 mCRPC 患者的镭治疗反应评估中的应用。
在这项前瞻性、多中心的成像发现研究中，2019 年至 2022 年期间纳入了 28 名符合镭治疗条件的 mCRPC 患者。患者按照标准护理接受镭治疗。研究程序包括 CT、骨闪烁扫描和 Ga-PSMA PET/CT，分别在基线时、镭治疗 3 个周期后和 6 个周期后以及治疗失败时进行。在所有 3 种影像学方法上对镭治疗的反应进行了视觉评估。在 Ga-PSMA PET/CT 上确定骨内总肿瘤体积（TTV）。使用新开发的图像配准工具研究了 PET/CT 连续图像的患者内异质性。结果与无进展生存（良好反应者与不良反应者；截止值为 24 周）和第 3 个周期后的碱性磷酸酶（ALP）反应进行了比较。
在 Ga-PSMA PET/CT 和骨闪烁扫描上，视觉反应评估标准无法区分良好反应者和不良反应者。对于 Ga-PSMA PET/CT，基线时良好反应者的 TTV 低于不良反应者，而两组在治疗期间 TTV 均增加。在镭治疗期间出现新的骨外转移的患者中，TTV 更高。虽然 TTV 和 ALP 在基线时相关，但治疗过程中 TTV 和 ALP 的变化没有相关性。在大多数患者中，Ga-PSMA 对 TTV 的反应表现出患者内异质性。
mCRPC 患者在 Ga-PSMA PET/CT 上的 TTV 较低，在接受镭治疗后具有最佳的临床结局。在大多数患者中，反应具有高度异质性。大多数患者中发生的 ALP 下降与 TTV 下降无关，这可能使人们对 ALP 在临床实践中监测镭治疗期间疾病的价值产生疑问。
