Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
Radiat Oncol. 2023 Jun 19;18(1):103. doi: 10.1186/s13014-023-02288-3.
This study examined the differences in late gastrointestinal (GI) toxicities in moderately hypofractionated intensity-modulated radiation therapy (IMRT) for locally advanced pancreatic ductal adenocarcinoma (LA-PDAC) by changing the planning organs at risk volume (PRV) margin and the target matching method and assessed the causes of adverse events.
We examined 37 patients with LA-PDAC who underwent moderately hypofractionated IMRT between 2016 and 2020 at our institution; 23 patients were treated with wide PRV margins and soft tissue matching (Protocol A) and 14 with narrow PRV margins and fiducial marker matching (Protocol B). The GI toxicities, local control (LC) rate, and overall survival (OS) were assessed for each protocol. The initially planned and daily doses to the gross tumor volume (GTV), stomach, and duodenum, reproduced from cone-beam computed tomography, were evaluated.
The late GI toxicity rate of grades 3-4 was higher in Protocol B (42.9%) than in Protocol A (4.3%). Although the 2-year LC rates were significantly higher in Protocol B (90.0%) than in Protocol A (33.3%), no significant difference was observed in OS rates. In the initial plan, no deviations were found for the stomach and duodenum from the dose constraints in either protocol. In contrast, daily dose evaluation for the stomach to duodenal bulb revealed that the frequency of deviation of V per session was 44.8% in Protocol B, which was significantly higher than the 24.3% in Protocol A.
Reducing PRV margins with fiducial marker matching increased GI toxicities in exchange for improved LC. Daily dose analysis indicated the trade-off between the GTV dose coverage and the irradiated doses to the GI. This study showed that even with strict matching methods, the PRV margin could not be reduced safely because of GI inter-fractional error, which is expected to be resolved with online adaptive radiotherapy.
本研究通过改变计划靶区（PRV）边界和靶区匹配方法，比较了局部晚期胰腺导管腺癌（LA-PDAC）适度分割调强放疗（IMRT）中晚期胃肠道（GI）毒性的差异，并评估了不良事件的原因。
我们检查了 2016 年至 2020 年在我院接受适度分割 IMRT 的 37 例 LA-PDAC 患者；23 例患者采用宽 PRV 边界和软组织匹配（方案 A），14 例患者采用窄 PRV 边界和基准标记匹配（方案 B）。评估每个方案的 GI 毒性、局部控制率（LC）和总生存率（OS）。从锥形束 CT 重建评估 GTV、胃和十二指肠的初始计划和每日剂量。
方案 B（42.9%）的晚期 GI 毒性 3-4 级发生率高于方案 A（4.3%）。尽管方案 B 的 2 年 LC 率（90.0%）明显高于方案 A（33.3%），但 OS 率无显著差异。在初始计划中，两个方案中胃和十二指肠均未超过剂量限制。相比之下，每日剂量评估显示，方案 B 中胃至十二指肠球部的 V 每节偏差频率为 44.8%，明显高于方案 A 的 24.3%。
使用基准标记匹配减少 PRV 边界会增加 GI 毒性，但可以提高 LC。每日剂量分析表明，GTV 剂量覆盖与 GI 照射剂量之间存在权衡。本研究表明，即使采用严格的匹配方法，由于 GI 分次误差，PRV 边界也不能安全缩小，这有望通过在线自适应放疗来解决。
