Lan Tien-Li, Lin Ko-Han, Chen Yi-Wei, Ono Koji, Kuo Chao-Yang, Peir Jinn-Jer, Hsu Shih-Ming
Department of Heavy Particles and Radiation Oncology, Taipei Veterans General Hospital.
School of Medicine, National Yang Ming Chiao Tung University.
Clin Nucl Med. 2025 Jul 8. doi: 10.1097/RLU.0000000000006047.
Boron Neutron Capture Therapy (BNCT) has gained popularity in recent years, with over 500 treatment courses performed in Taiwan since 2017. Traditionally, the tumor-to-normal tissue ratio (T/N ratio) is assessed using SUV measurements from 4-borono-2-(18) F-fluoro-phenylalanine (F-BPA) PET, allowing for precise tumor boron concentration estimation when serum boron levels are measured on the day of treatment. However, limited accessibility to F-BPA PET complicates dose calculations, and in its absence, a fixed T/N ratio of 3 is used in treatment planning. Fluciclovine PET has recently been explored as an alternative, as both fluciclovine and BPA share the L-type amino acid transporter 1 (LAT-1) transporter, although fluciclovine can also be transported via alanine-serine-cysteine transporter 2 (ASCT2). However, its accuracy in reflecting BPA distribution and its correlation with treatment response remain uncertain.
Since June 2022, fluciclovine PET has been used for brain tumor evaluation in Taiwan. By June 2024, 80 brain tumor patients underwent pre-BNCT assessment with fluciclovine PET. After excluding those who received a second treatment course, 44 patients were analyzed. The average T/N ratio in this cohort was 4.6, higher than reported averages for F-BPA PET (2.5 for head and neck tumors, 3 for brain tumors). The tumor response rate was defined as patients achieving either a complete or partial response, as evaluated by experienced neuroradiologists. Patients were categorized based on response achievement, and potential prognostic factors were compared.
The mean T/N ratio of fluciclovine PET was 4.61±1.43 (range: 2.58-8.86). Among 15 patients who underwent follow-up fluciclovine PET 3 months post-BNCT, the mean T/N ratio decreased significantly to 2.85±1.16 (range: 1.00-5.47). Treatment response assessment at 3 months post-BNCT revealed that 4 patients achieved complete response (CR), 26 had partial response (PR), 5 exhibited stable disease (SD), and 9 experienced progressive disease (PD). Responders had significantly smaller tumors compared with nonresponders (35.74 vs. 83.83 cm³, p=0.009) and received higher minimum tumor doses (18.50 vs. 12.13 GyE, p=0.033). In addition, a significant decline in T/N ratio was observed following BNCT, decreasing from 4.602±0.368 pretreatment to 2.847±0.300 at 3 months post-treatment.
Our findings suggest that while fluciclovine PET may provide an estimate of BPA uptake, it is not a reliable predictor of treatment response. However, it remains an effective tool for assessing treatment effect following BNCT. Further studies are necessary to identify key prognostic factors for selecting BNCT candidates and to determine whether fluciclovine PET can effectively predict BNCT outcomes.
硼中子俘获疗法（BNCT）近年来颇受关注，自2017年以来台湾已开展了500多个疗程的治疗。传统上，肿瘤与正常组织比值（T/N比值）通过4-硼基-2-（18）F-氟苯丙氨酸（F-BPA）PET的SUV测量值来评估，在治疗当天测量血清硼水平时可精确估算肿瘤硼浓度。然而，F-BPA PET的可及性有限使剂量计算变得复杂，在缺乏该检查时，治疗计划中使用固定的T/N比值3。氟代脱氧胸苷PET最近被探索作为一种替代方法，因为氟代脱氧胸苷和BPA都共享L型氨基酸转运体1（LAT-1）转运体，尽管氟代脱氧胸苷也可通过丙氨酸-丝氨酸-半胱氨酸转运体2（ASCT2）转运。然而，其反映BPA分布的准确性及其与治疗反应的相关性仍不确定。
自2022年6月起，台湾将氟代脱氧胸苷PET用于脑肿瘤评估。截至2024年6月，80例脑肿瘤患者接受了氟代脱氧胸苷PET的BNCT前评估。排除接受过第二个疗程治疗的患者后，对44例患者进行分析。该队列的平均T/N比值为4.6，高于F-BPA PET报告的平均值（头颈部肿瘤为2.5，脑肿瘤为3）。肿瘤反应率定义为经经验丰富的神经放射科医生评估达到完全或部分缓解的患者。根据反应达成情况对患者进行分类，并比较潜在的预后因素。
氟代脱氧胸苷PET的平均T/N比值为4.61±1.43（范围：2.58 - 8.86）。在15例BNCT后3个月接受随访氟代脱氧胸苷PET检查的患者中，平均T/N比值显著降至2.85±1.16（范围：1.00 - 5.47）。BNCT后3个月的治疗反应评估显示，4例患者达到完全缓解（CR），26例部分缓解（PR），5例疾病稳定（SD），9例疾病进展（PD）。反应者的肿瘤明显小于无反应者（35.74 vs. 83.83 cm³，p = 0.009），且接受的最小肿瘤剂量更高（18.50 vs. 12.13 GyE，p = 0.033）。此外，BNCT后观察到T/N比值显著下降，从治疗前的4.602±0.368降至治疗后3个月的2.847±0.300。
我们的研究结果表明，虽然氟代脱氧胸苷PET可能提供BPA摄取的估计值，但它不是治疗反应的可靠预测指标。然而，它仍然是评估BNCT后治疗效果的有效工具。需要进一步研究以确定选择BNCT候选者的关键预后因素，并确定氟代脱氧胸苷PET是否能有效预测BNCT结果。
