Kaiser Adeel, Luther Nicole, Mittauer Kathryn E, Gul Amna, Herrera Robert A, Roy Mukesh K, Fellows Ashley, Rzepczynski Amy, Deere Will, Hall Matthew D, Kotecha Rupesh, Bassiri-Gharb Nema, Gutierrez Alonso N, Chuong Michael D
Department of Radiation Oncology, Miami Cancer Institute, Miami, FL 33176, USA.
Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA.
Cancers (Basel). 2025 Jun 20;17(13):2061. doi: 10.3390/cancers17132061.
Non-ablative stereotactic body radiation therapy (SBRT) is commonly employed for locally advanced pancreatic cancer (LAPC) using computed tomography-guided radiotherapy (CTgRT) without online adaptive radiation therapy (oART). The safe delivery of ablative SBRT has been demonstrated using stereotactic magnetic resonance-guided online adaptive radiation therapy (SMART). We performed an in silico comparison of non-adapted CTgRT versus SMART to better understand the potential benefit of oART for ablative pancreatic SBRT. We retrospectively evaluated original and daily adapted SMART plans that were previously delivered for 20 consecutive LAPC cases (120 total plans across all patients) treated on a 0.35 T MR-linac prescribed to 50 Gy (gross disease) and 33 Gy (elective sites) simultaneously in five fractions. Six comparative CTgRT plans for each patient (one original, five daily treatment) were retrospectively generated with the same prescribed dose and planning parameters as the SMART plans assuming no oART availability. The impact of daily anatomic changes on CTgRT and SMART plans without oART was evaluated across each treatment day MRI scan acquired for SMART. Ninety percent of cases involved the pancreatic head. No statistically significant differences were seen between CTgRT and SMART with respect to target coverage. Nearly all (96%) fractions planned on either CT or MRI platforms exceeded at least one GI organ at risk (OAR) constraint without oART. Significant differences favoring SMART over non-adaptive CTgRT were observed for the duodenum V35 Gy ≤ 0.5 cc (34.2 vs. 41.9 Gy, = 0.0035) and duodenum V40 Gy ≤ 0.03 cc (37 vs. 52.5 Gy, = 0.0006) constraints. Stomach V40 Gy trended towards significance favoring SMART (37 vs. 40.3 Gy, = 0.057) while no significant differences were seen. This is the first study that quantifies the frequency and extent of GI OAR constraint violations that would occur during ablative five-fraction SBRT using SMART vs. CTgRT. GI OAR constraint violations are expected for most fractions without oART whereas all constraints can be achieved with oART. As such, these data suggest that oART should be required for ablative five-fraction pancreatic SBRT.
非消融性立体定向体部放射治疗（SBRT）通常用于局部晚期胰腺癌（LAPC），采用计算机断层扫描引导放疗（CTgRT）且不进行在线自适应放疗（oART）。使用立体定向磁共振引导在线自适应放疗（SMART）已证明了消融性SBRT的安全实施。我们进行了非适应性CTgRT与SMART的计算机模拟比较，以更好地了解oART对消融性胰腺SBRT的潜在益处。我们回顾性评估了先前为20例连续的LAPC病例（所有患者共120个计划）实施的原始和每日适应性SMART计划，这些病例在0.35T MR直线加速器上接受治疗，同时分五剂给予50Gy（大体肿瘤）和33Gy（选择性部位）的处方剂量。假设没有oART可用，为每位患者回顾性生成六个对比CTgRT计划（一个原始计划，五个每日治疗计划），其处方剂量和计划参数与SMART计划相同。在为SMART获取的每次治疗日MRI扫描中，评估每日解剖变化对无oART的CTgRT和SMART计划的影响。90%的病例累及胰头。在靶区覆盖方面，CTgRT和SMART之间未观察到统计学显著差异。在无oART的情况下，在CT或MRI平台上计划的几乎所有（96%）分次至少超过一个胃肠道危及器官（OAR）的限制。在十二指肠V35Gy≤0.5cc（34.2对41.9Gy，P = 0.0035）和十二指肠V40Gy≤0.03cc（37对52.5Gy，P = 0.0006）限制方面，观察到有利于SMART而非非适应性CTgRT的显著差异。胃V40Gy倾向于有利于SMART的显著性（37对40.3Gy，P = 0.057），但未观察到显著差异。这是第一项量化使用SMART与CTgRT进行消融性五分次SBRT期间胃肠道OAR限制违反的频率和程度的研究。在无oART的情况下，大多数分次预计会出现胃肠道OAR限制违反，而有oART时所有限制均可实现。因此，这些数据表明消融性五分次胰腺SBRT应需要oART。
