目的：68Ga标记的成纤维细胞激活蛋白抑制剂（FAPI）是一种新型PET示踪剂，在胰腺癌分期方面具有巨大潜力。关于局部晚期或复发性疾病的数据很少，特别是关于高剂量放化疗 (CRT) 之前和之后示踪剂摄取的数据。本研究的目的是评估这种情况下的 [68Ga]Ga-FAPI-46 PET/CT 分期。方法：27 例化疗后疾病稳定或部分缓解的局部复发或局部晚期胰腺腺癌（LRPAC n = 15，LAPAC n = 12）患者接受 FAPI PET/CT 并接受 M0 期巩固 CRT 并随访 FAPI每三个月进行 PET/CT 一次，直至全身进展。在基线和后续 PET/CT 扫描中测量定量 PET 参数 SUVmax、SUVmean、FAPI 衍生的肿瘤体积和总病灶 FAPI 摄取。对增强 CT (ceCT) 和 PET/CT 数据进行盲法评估，并根据 TNM 分类进行分期。结果：在 27 名基线患者中，有 23 名患者中的 23 名患者中，与单独使用 ceCT 相比，FAPI PET/CT 改进了分期，导致 52% 的患者发生重大治疗改变（30%：由于 N 降期而调整目标体积，15%：改用姑息性全身治疗）仅因弥漫性转移而化疗，7%：因其他原因而流产放疗）。关于随访扫描，在 24 次随访扫描中有 11 次 (46%) 注意到进行 FAPI PET/CT 后的主要治疗改变，由于 M 升期和远处淋巴结消融性放疗而转为全身化疗或最佳支持治疗寡转移。出乎意料的是，在超过 90% 的后续扫描中，放疗并未诱导局部纤维化相关的 FAPI 摄取。在第一次随访期间，所有定量 PET 指标均下降，并且与局部失败相比，受照射病灶在局部控制疾病中的 FAPI 摄取显着降低（SUVmax p = 0.047，SUVmean p = 0.0092）。结论：与 ceCT 相比，FAPI PET/CT 导致 LRPAC 和 LAPAC 患者放疗前后发生重大治疗改变，这可能有助于识别从每个治疗阶段的调整中受益的患者。 FAPI PET/CT 应被视为 CRT 前后 LRPAC 或 LAPAC 的有用诊断工具。© 作者。

Purpose: 68Ga-labeled fibroblast activation protein inhibitor (FAPI) is a novel PET tracer with great potential for staging pancreatic cancer. Data on locally advanced or recurrent disease is sparse, especially on tracer uptake before and after high dose chemoradiotherapy (CRT). The aim of this study was to evaluate [68Ga]Ga-FAPI-46 PET/CT staging in this setting. Methods: Twenty-seven patients with locally recurrent or locally advanced pancreatic adenocarcinoma (LRPAC n = 15, LAPAC n = 12) in stable disease or partial remission after chemotherapy underwent FAPI PET/CT and received consolidation CRT in stage M0 with follow-up FAPI PET/CT every three months until systemic progression. Quantitative PET parameters SUVmax, SUVmean, FAPI-derived tumor volume and total lesion FAPI-uptake were measured in baseline and follow-up PET/CT scans. Contrast-enhanced CT (ceCT) and PET/CT data were evaluated blinded and staged according to TNM classification. Results: FAPI PET/CT modified staging compared to ceCT alone in 23 of 27 patients in baseline, resulting in major treatment alterations in 52% of all patients (30%: target volume adjustment due to N downstaging, 15%: switch to palliative systemic chemotherapy only due to diffuse metastases, 7%: abortion of radiotherapy due to other reasons). Regarding follow-up scans, major treatment alterations after performing FAPI PET/CT were noted in eleven of 24 follow-up scans (46%) with switch to systemic chemotherapy or best supportive care due to M upstaging and ablative radiotherapy of distant lymph node and oligometastasis. Unexpectedly, in more than 90 % of the follow-up scans, radiotherapy did not induce local fibrosis related FAPI uptake. During the first follow-up, all quantitative PET metrics decreased, and irradiated lesions showed significantly lower FAPI uptake in locally controlled disease (SUVmax p = 0.047, SUVmean p = 0.0092) compared to local failure. Conclusion: Compared to ceCT, FAPI PET/CT led to major therapeutic alterations in patients with LRPAC and LAPAC prior to and after radiotherapy, which might help identify patients benefiting from adjustments in every treatment stage. FAPI PET/CT should be considered a useful diagnostic tool in LRPAC or LAPAC before and after CRT.© The author(s).