Background: One of the challenges in treating pancreatic ductal adenocarcinoma (PDAC) with stereotactic radiotherapy (SRT) is to manage lesions abutted to the duodenum, bowel and stomach. Simultaneous integrated protection (SIP) is one of the proposed approaches to increase plan reproducibility and quality. However, no clinical data are available regarding the dosimetric objectives impacting local control probability.Methods: This is a prospective, single-arm study. Key inclusion criteria were as follows: PDAC histology; tumor abutment with duodenum, stomach, or small bowel; and SRT schedule consisting of 45 Gy in six fractions. Delineation of the PTV overlapped with critical OARs (PTV_SIP) and PTV outside critical OARs (PTV_Dominant) was mandatory. Dose constraints were as follows: (near) maximum dose, D2cc, and D20cc to critical OARs 38 Gy, 32 Gy, and 24 Gy, respectively. This study was designed to prospectively investigate the main clinical and dosimetric parameters impacting freedom from local recurrence (FFLR).Results: From June 2019 to January 2024, 104 patients were enrolled. One-year FFLR was 91.7%. Fifteen events of local failure occurred (17.6%). Mapping of local relapses showed a relapse inside the PTV_SIP area in nine patients and outside the PTV_SIP in six cases (NS). Whole PTV > 69 cc, PTV_SIP > 4 cc, PTV-SIP/whole PTV ratio > 7%, (near) Dmin to PTV_SIP < 25 Gy, mean dose to PTV_SIP < 28 Gy, and (near) Dmin to PTV_Dominant < 29 Gy were associated with worse FFLR. Multivariable analysis showed PTV_SIP absolute volume of more than 4 cc, mean dose to PTV_SIP < 28 Gy and whole PTV > 69 cc were independently related to worse FFLR. One case of acute G4 toxicity and two cases of acute G3 toxicity occurred, with two late toxicity deaths not certainly due to treatment.Conclusions: In this prospective study, SIP planning strategy with six fractions is safe and effective in pancreatic targets with critical contact with critical OARs. Given its potential advantages, SIP planning is a potential innovative strategy that should be compared to standard SRT planning in an ad hoc trial design.
背景：采用立体定向放射治疗（SRT）治疗胰腺导管腺癌（PDAC）的挑战之一在于处理与十二指肠、肠道和胃紧密相邻的病灶。同步整合保护（SIP）是提高计划可重复性和质量的建议方法之一。然而，目前尚无关于影响局部控制概率的剂量学目标的临床数据。 方法：本研究为前瞻性单臂研究。主要纳入标准如下：PDAC组织学确诊；肿瘤与十二指肠、胃或小肠相邻；SRT方案为6次分割共45 Gy。必须勾画与关键危及器官（OARs）重叠的计划靶区（PTV_SIP）以及位于关键OARs外的计划靶区（PTV_Dominant）。剂量限制如下：关键OARs的（近）最大剂量、D2cc和D20cc分别为38 Gy、32 Gy和24 Gy。本研究旨在前瞻性探讨影响无局部复发生存（FFLR）的主要临床和剂量学参数。 结果：2019年6月至2024年1月期间，共纳入104例患者。一年FFLR为91.7%。发生15例局部失败事件（17.6%）。局部复发分布显示：9例患者复发位于PTV_SIP区域内，6例位于PTV_SIP区域外（无统计学意义）。全PTV > 69 cc、PTV_SIP > 4 cc、PTV_SIP/全PTV比值 > 7%、PTV_SIP（近）最小剂量 < 25 Gy、PTV_SIP平均剂量 < 28 Gy以及PTV_Dominant（近）最小剂量 < 29 Gy与较差的FFLR相关。多变量分析显示，PTV_SIP绝对体积 > 4 cc、PTV_SIP平均剂量 < 28 Gy和全PTV > 69 cc与较差的FFLR独立相关。发生1例急性4级毒性和2例急性3级毒性，2例晚期毒性死亡不能完全归因于治疗。 结论：在这项前瞻性研究中，对于与关键OARs紧密接触的胰腺靶区，采用6次分割的SIP计划策略安全有效。鉴于其潜在优势，SIP计划是一种潜在的创新策略，应在专门设计的试验中与标准SRT计划进行比较。
肿瘤(癌症)患者之家