Purpose or Objective: To evaluate the feasibility and clinical utility of integrating sequential PSMA-PET imaging into an offline–online adaptive workflow for response-based dominant intraprostatic lesion (DIL)-boosting high-risk prostate cancer treated with stereotactic ablative radiotherapy (SABR). Materials and Methods: As part of a prospective trial, patients were treated on MR- or CBCT-guided adaptive radiotherapy (ART) systems with prostate/pelvic node 5-fraction SABR (36.25 Gy/25 Gy) with DIL boost (50 Gy). Whereas traditional DIL boost volumes delineate full pre-therapy imaging-defined disease (GTVinitial), this study serially refined DIL boost volumes based on treatment response defined by PSMA-PET scans after neoadjuvant androgen deprivation therapy (nADT, GTVmb1) and fraction 3 SABR (GTVmb2). DIL delineation employed PET-PSMA fusion to CT/MR simulation and was guided by a rule-based %SUVmax threshold approach. Comparisons of GTV volumes and OAR dosimetry were performed between plans using GTVinitial versus GTVmb1/GTVmb2 for DIL boost, for each of the initial cohorts of five patients from the initially treated cohorts. Results: Five patients treated on MR-Linac (n= 3) or CBCT-based ART (n= 2) were analyzed. Three patients exhibited complete imaging response after nADT, omitting GTVmb boosts. Offline GTVmb refinements based on PSMA-PET were seamlessly integrated into ART workflows without introducing additional treatment time. DIL GTV volumes significantly decreased (p= 0.03) from an initial mean of 11.4 cc (GTVinitial) to 4.1 cc (GTVmb1) and 3.0 cc (GTVmb2). Dosimetric analysis showed meaningful reductions in OAR doses: rectal wall D0.035 cc decreased by up to 12 Gy, while bladder wall D0.035 cc and V18.3 Gy reduced from 52.3 Gy and 52.3 cc (Plan_initial) to 42.9 Gy and 24.9 cc (Plan_mb2), respectively. Urethra doses remained stable, with minor reductions. Sigmoid and femoral head doses remained within acceptable limits. Online adaptation efficiently addressed daily anatomical variations, enabling simulation-free plan re-optimization. Conclusion: PSMA-PET-guided adaptive microboosting for HRPCa SABR is feasible and effective. Standard MR-Linac and CBCT systems offer practical alternatives to BgRT platforms, enabling biology-driven dose personalization and potentially reducing toxicity.
目的或目标：评估将序贯PSMA-PET成像整合至离线-在线自适应工作流程中，用于基于治疗反应的靶区内病灶强化治疗高危前列腺癌立体定向消融放疗的可行性及临床效用。 材料与方法：作为一项前瞻性试验的一部分，患者接受MR或CBCT引导的自适应放疗系统治疗，方案为前列腺/盆腔淋巴结5分次立体定向消融放疗（36.25 Gy/25 Gy）联合靶区内病灶强化（50 Gy）。传统靶区内病灶强化靶区勾画基于治疗前影像定义的完整病灶范围，本研究则根据新辅助雄激素剥夺治疗后及第3分次立体定向消融放疗后的PSMA-PET扫描所定义的治疗反应，序贯优化强化靶区。靶区勾画采用PSMA-PET与CT/MR模拟影像融合，并基于规则的%SUVmax阈值方法进行指导。在初始治疗的5例患者队列中，比较了使用传统靶区与优化后靶区进行病灶强化时的靶区体积和危及器官剂量学差异。 结果：分析了5例接受MR直线加速器或CBCT引导自适应放疗的患者。3例患者在新辅助雄激素剥夺治疗后出现完全影像学缓解，未进行优化后靶区强化。基于PSMA-PET的离线靶区优化可无缝整合至自适应放疗工作流程，未增加额外治疗时间。靶区内病灶体积从初始平均11.4 cc显著减小至4.1 cc和3.0 cc。剂量学分析显示危及器官剂量显著降低：直肠壁D0.035cc降低达12 Gy，膀胱壁D0.035cc和V18.3 Gy分别从52.3 Gy和52.3 cc降至42.9 Gy和24.9 cc。尿道剂量保持稳定，略有降低。乙状结肠和股骨头剂量均在可接受范围内。在线自适应有效处理了每日解剖结构变化，实现了无需重新模拟的计划再优化。 结论：PSMA-PET引导的自适应微强化治疗高危前列腺癌立体定向消融放疗具有可行性和有效性。标准MR直线加速器和CBCT系统为BgRT平台提供了实用替代方案，可实现生物学驱动的剂量个体化，并可能降低治疗毒性。
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