Department of Oncology, Aarhus University Hospital, Denmark.
Danish Center for Particle Therapy, Aarhus University Hospital, Denmark.
Radiother Oncol. 2022 Aug;173:102-108. doi: 10.1016/j.radonc.2022.05.038. Epub 2022 Jun 3.
The aim was to evaluate and compare the dosimetric effect and robustness towards day-to-day anatomical and setup variations in the delivered dose for photon and proton treatments of sinonasal cancer (SNC) patients.
Photon (VMAT) and proton (IMPT) plans were optimized retrospectively for 24 SNC patients. Synthetic CTs (synCT) were obtained by deforming the planning CT (pCT) to the anatomy of every daily cone-beam CT. Both VMAT and IMPT plans were recalculated on the synCTs. The recalculated daily dose was accumulated over the whole treatment on the pCT. Target coverage and dose to organs and risk (OARs) were evaluated for all patients for the nominal, daily and accumulated dose distribution.
In general, dose to OARs farther away from the target, including brain, chiasm and contralateral optic nerve, was lower for proton plans than photon plans. Whereas, OARs in proximity of the target received a lower dose for photon plans. For proton plans, the target coverage (volume of CTV receiving 95% of prescribed dose), V95%, fell below 99% for 9/24 patients in one or more fractions. For photon plans, 4/24 patients had one or more fractions where V95% fell below 99%. For accumulated doses, V95% was below 99% only in two cases, but above 98% for all patients.
Photon and proton treatment have different strengths regarding OAR sparing. The robustness was high for both treatment modalities. Patient selection for either proton or photon radiation therapy of SNC patients should be based on a case-by-case comparison.
本研究旨在评估并比较光子和质子治疗鼻窦癌（SNC）患者的剂量学效应，并比较在每日解剖结构和治疗摆位变化下，两种治疗方式的剂量分布的稳健性。
我们回顾性地为 24 例 SNC 患者优化了光子（VMAT）和质子（IMPT）计划。通过将计划 CT（pCT）变形到每日锥形束 CT 的解剖结构，获得了合成 CT（synCT）。我们在 synCT 上重新计算了 VMAT 和 IMPT 计划。将整个治疗过程中的每日剂量累积到 pCT 上。我们对所有患者的名义剂量、每日剂量和累积剂量分布进行了靶区覆盖和危及器官（OAR）剂量评估。
一般来说，质子计划的 OAR 剂量（包括脑、视交叉和对侧视神经）比光子计划低，这些 OAR 离靶区较远。而对于靶区附近的 OAR，光子计划的剂量较低。对于质子计划，9/24 例患者的 1 个或多个分次的靶区覆盖率（CTV 接受 95%处方剂量的体积，V95%）低于 99%。对于光子计划，4/24 例患者的 1 个或多个分次的 V95%低于 99%。对于累积剂量，只有 2 例患者的 V95%低于 99%，但所有患者均高于 98%。
光子和质子治疗在保护 OAR 方面各有优势。两种治疗方式的稳健性都很高。对于 SNC 患者，应根据具体情况选择质子或光子放射治疗。
