Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany.
Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany; Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany.
Radiother Oncol. 2021 Jul;160:192-201. doi: 10.1016/j.radonc.2021.04.016. Epub 2021 May 1.
Adenoid cystic carcinomas (ACCs) are rare epithelial tumors mostly situated in the head and neck region and characterized by infiltrative growth. The tumor stroma of ACCs includes cancer-associated fibroblasts (CAFs) expressing Fibroblast Activation Protein (FAP), a new target for positron emission tomography (PET) imaging. Here we describe the value of PET/ computed tomography (PET/CT) imaging using Ga-labelled FAP-Inhibitors (Ga-FAPI-PET/CT) and their clinical potential for staging and radiotherapy planning in 12 ACC patients (7 primary, 5 recurrent).
Patients underwent contrast enhanced staging CT (ceCT) and magnetic resonance imaging (ceMRI) before Ga-FAPI - PET/CT. PET-scans were acquired 10, 60 and 180 minutes after administration of 150-250 MBq of Ga-labelled FAPI tracers. SUV and SUV values of ACCs and healthy organs were obtained using a 60% of maximum iso-contour. FAP and alpha smooth muscle actin (α-SMA) immunohistochemistry was performed in 13 cases (3 with and 10 without Ga FAPI-PET/CT). Staging and radiotherapy planning based on Ga-FAPI-PET/CT versus ceCT/MRI alone were compared.
We observed elevated tracer uptake in all ACCs. Immunohistochemistry showed FAP-expressing CAFs in the tumor. Compared to conventional staging, Ga-FAPI-PET/CT led to upstaging in 2/12 patients and to detection of additional metastases in 3 patients, thus in total 42% of patients had their staging altered. Moreover, Ga-FAPI PET improved the accuracy of target volume delineation for radiotherapy, as compared to CT and MRI.
Ga-FAPI-PET/CT is a promising imaging modality for ACC, increasing the accuracy of staging exams and radiotherapy planning volumes, as compared conventional to CT and MRI.
腺样囊性癌（ACC）是一种罕见的上皮肿瘤，主要发生在头颈部，其特征是浸润性生长。ACC 的肿瘤基质包括表达成纤维细胞激活蛋白（FAP）的癌相关成纤维细胞（CAF），FAP 是正电子发射断层扫描（PET）成像的新靶点。在这里，我们描述了使用 Ga 标记的 FAP 抑制剂（Ga-FAPI-PET/CT）进行 PET/计算机断层扫描（PET/CT）成像的价值，并描述了其在 12 例 ACC 患者（7 例原发性，5 例复发性）中的分期和放疗计划的临床潜力。
患者在 Ga-FAPI-PET/CT 前进行了增强对比 CT（ceCT）和磁共振成像（ceMRI）检查。在注射 150-250 MBq Ga 标记的 FAPI 示踪剂后 10、60 和 180 分钟采集 PET 扫描。使用 60%的最大等浓度轮廓线获得 ACC 和健康器官的 SUV 和 SUV 值。在 13 例患者中进行了 FAP 和α平滑肌肌动蛋白（α-SMA）免疫组织化学检查（3 例有 Ga FAPI-PET/CT，10 例无 Ga FAPI-PET/CT）。比较了基于 Ga-FAPI-PET/CT 与单独 ceCT/MRI 的分期和放疗计划。
我们观察到所有 ACC 中都有升高的示踪剂摄取。免疫组化显示肿瘤中存在表达 FAP 的 CAF。与常规分期相比，Ga-FAPI-PET/CT 在 2/12 例患者中导致分期升高，在 3 例患者中检测到额外转移，因此总共有 42%的患者分期改变。此外，与 CT 和 MRI 相比，Ga-FAPI PET 提高了放疗靶区勾画的准确性。
Ga-FAPI-PET/CT 是一种很有前途的 ACC 成像方式，与常规 CT 和 MRI 相比，它可以提高分期检查和放疗计划体积的准确性。
