Martin Fanny, Magnier Florian, Berger Lucie, Miroir Jessica, Chautard Emmanuel, Verrelle Pierre, Lapeyre Michel, Biau Julian
Department of Radiotherapy, Centre Jean Perrin, 63011, Clermont-Ferrand, France.
Department of Medical Physics, Centre Jean Perrin, 63011, Clermont-Ferrand, France.
Radiat Oncol. 2016 Apr 18;11:58. doi: 10.1186/s13014-016-0632-8.
Benign tumors of the skull base are a challenge when delivering radiotherapy. An appropriate choice of radiation technique may significantly improve the patient's outcomes. Our study aimed to compare the dosimetric results of fractionated stereotactic radiotherapy between non-coplanar dynamic arcs and coplanar volumetric modulated arctherapy (Rapidarc®).
Thirteen patients treated with Novalis TX® were analysed: six vestibular schwannomas, four pituitary adenomas and three meningioma. Two treatment plans were created for each case: dynamic arcs (4-5 non coplanar arcs) and Rapidarc® (2 coplanar arcs). All tumors were >3 cm and accessible to both techniques. Patients had a stereotactic facemask (Brainlab) and were daily repositioned by Exactrac®. GTV and CTV were contoured according to tumor type. A 1-mm margin was added to the CTV to obtain PTV. Radiation doses were 52.2-54 Gy, using 1.8 Gy per fraction. Treatment time was faster with Rapidarc®.
The mean PTV V95 % was 98.8 for Rapidarc® and 95.9 % for DA (p = 0.09). Homogeneity index was better with Rapidarc®: 0.06 vs. 0.09 (p = 0.01). Higher conformity index values were obtained with Rapidarc®: 75.2 vs. 67.9 % (p = 0.04). The volume of healthy brain that received a high dose (V90 %) was 0.7 % using Rapidarc® vs. 1.4 % with dynamic arcs (p = 0.05). Rapidarc® and dynamic arcs gave, respectively, a mean D40 % of 10.5 vs. 18.1 Gy (p = 0.005) for the hippocampus and a Dmean of 25.4 vs. 35.3 Gy (p = 0.008) for the ipsilateral cochlea. Low-dose delivery with Rapidarc® and dynamic arcs were, respectively, 184 vs. 166 cm(3) for V20 Gy (p = 0.14) and 1265 vs. 1056 cm(3) for V5 Gy (p = 0.67).
Fractionated stereotactic radiotherapy using Rapidarc® for large benign tumors of the skull base provided target volume coverage that was at least equal to that of dynamics arcs, with better conformity and homogeneity and faster treatment time. Rapidarc® also offered better sparing of the ipsilateral cochlea and hippocampus. Low-dose delivery were similar between both techniques.
颅底良性肿瘤在进行放射治疗时具有挑战性。选择合适的放射技术可能会显著改善患者的治疗效果。我们的研究旨在比较非共面动态弧形放疗与共面容积调强弧形放疗（Rapidarc®）在分次立体定向放疗中的剂量学结果。
对13例接受Novalis TX®治疗的患者进行分析：6例前庭神经鞘瘤、4例垂体腺瘤和3例脑膜瘤。为每个病例制定两个治疗计划：动态弧形放疗（4 - 5个非共面弧形）和Rapidarc®（2个共面弧形）。所有肿瘤直径均大于3 cm，两种技术均可实施治疗。患者佩戴立体定向面罩（Brainlab），并通过Exactrac®进行每日体位重复定位。根据肿瘤类型勾画GTV和CTV。在CTV周围添加1 mm的边界以获得PTV。放射剂量为52.2 - 54 Gy，每次分割剂量为1.8 Gy。使用Rapidarc®时治疗时间更快。
Rapidarc®的平均PTV V95%为98.8%，动态弧形放疗（DA）为95.9%（p = 0.09）。Rapidarc®的均匀性指数更好：0.06对比0.09（p = 0.01）。Rapidarc®获得的适形指数值更高：75.2%对比67.9%（p = 0.04）。接受高剂量（V90%）的健康脑组织体积，Rapidarc®为0.7%，动态弧形放疗为1.4%（p = 0.05）。Rapidarc®和动态弧形放疗分别使海马体的平均D40%为10.5 Gy对比18.1 Gy（p = 0.005），同侧耳蜗的平均Dmean为25.4 Gy对比35.3 Gy（p = 0.008）。Rapidarc®和动态弧形放疗的低剂量照射，V20 Gy分别为184 cm³对比166 cm³（p = 0.14），V5 Gy分别为1265 cm³对比1056 cm³（p = 0.67）。
对于颅底大型良性肿瘤，使用Rapidarc®进行分次立体定向放疗提供的靶区覆盖至少与动态弧形放疗相当，具有更好的适形性和均匀性，且治疗时间更快。Rapidarc®还能更好地保护同侧耳蜗和海马体。两种技术的低剂量照射情况相似。
