Eitan Tal, Damico Nicholas J, Pidikiti Rajesh, Kharouta Michael Z, Dobbins Donald, Jesseph Frederick B, Smith Mark, Mangla Ankit, Teknos Theodoros N, Mansur David B, Machtay Mitchell, Yao Min, Bhatt Aashish D
Case Western Reserve University School of Medicine, Cleveland, OH, USA.
Department of Radiation Oncology, University Hospitals Seidman Cancer Center at Case Western Reserve University, Cleveland, OH, USA.
Int J Part Ther. 2020 Winter;6(3):13-18. doi: 10.14338/IJPT-19-00074. Epub 2019 Dec 16.
Reirradiation in the scalp area can be challenging given the proximity to organs at risk (OARs), such as the eye and brain. Our aim is to evaluate the dosimetric differences of volumetric modulated arc therapy (VMAT) and electron beam therapy (EBT) compared with 3-dimensional proton beam therapy (PBT).
We evaluated a patient with recurrent angiosarcoma of the left temporal scalp after prior surgical resections and radiation therapy to 60 Gy in 30 fractions who needed reirradiation. We generated VMAT, EBT, and PBT plans using the Pinnacle Treatment Planning System (TPS). Both VMAT and EBT plans used a skin bolus, whereas no bolus was used for the proton plan. Doses to the OARs, including cochlea, eyes, lens, lacrimal glands, optic nerves, optic chiasm, pituitary gland, and underlying brain, were compared.
The reirradiation treatment dose was 60 Gy(RBE). Target volume coverage was comparable in all plans. Compared with VMAT and EBT, the PBT plan showed reductions in mean and maximum doses to all OARs. Without the use of protons, several OARs would have exceeded dose tolerance utilizing VMAT or electrons. Dose reduction of up to 100% was achieved for central and contralateral OARs.
Compared with VMAT and EBT, PBT resulted in dose reductions to all OARs, while maintaining excellent target coverage. PBT showed a significant advantage in treating superficially located skin cancers, such as angiosarcoma, without the need for a bolus. PBT can be considered in the upfront treatment and certainly in the reirradiation setting.
鉴于头皮区域临近如眼睛和大脑等危及器官（OARs），对该区域进行再程放疗具有挑战性。我们的目的是评估容积调强弧形放疗（VMAT）和电子束放疗（EBT）与三维质子束放疗（PBT）相比的剂量学差异。
我们评估了一名左颞部头皮血管肉瘤复发患者，该患者此前接受过手术切除及30次分割至60 Gy的放疗，现需要再程放疗。我们使用Pinnacle治疗计划系统（TPS）生成VMAT、EBT和PBT计划。VMAT和EBT计划均使用皮肤填充物，而质子计划未使用填充物。比较了包括耳蜗、眼睛、晶状体、泪腺、视神经、视交叉、垂体及深部脑组织等危及器官的剂量。
再程放疗剂量为60 Gy（相对生物学效应）。所有计划的靶区体积覆盖情况相当。与VMAT和EBT相比，PBT计划显示所有危及器官的平均剂量和最大剂量均降低。若不使用质子，使用VMAT或电子束时，多个危及器官的剂量将超过耐受剂量。中央及对侧危及器官的剂量降低高达100%。
与VMAT和EBT相比，PBT可降低所有危及器官的剂量，同时保持良好的靶区覆盖。PBT在治疗如血管肉瘤等浅表皮肤癌时具有显著优势，无需使用填充物。在初始治疗中，尤其是再程放疗时，可考虑使用PBT。
