Scafa Davide, Muedder Thomas, Holz Jasmin A, Koch David, Nour Younéss, Garbe Stephan, Gonzalez-Carmona Maria A, Feldmann Georg, Vilz Tim O, Köksal Mümtaz, Giordano Frank A, Schmeel Leonard Christopher, Sarria Gustavo R
Department of Radiation Oncology, University Hospital Bonn, Bonn, Germany.
Department of Internal Medicine I, University Hospital Bonn, Bonn, Germany.
Front Oncol. 2021 Dec 2;11:767468. doi: 10.3389/fonc.2021.767468. eCollection 2021.
PURPOSE/OBJECTIVES: To perform a dosimetric comparison between kilovoltage intraoperative radiotherapy (IORT) and stereotactic radiosurgery (SRS) simulating both deep-inspiration breath-hold (DIBH) and free-breathing (FB) modalities for patients with liver metastases.
METHODS/MATERIALS: Diagnostic computed tomographies (CT) of patients carrying one or two lesions <4 cm and who underwent surgery were retrospectively screened and randomly selected for the study. For DIBH-SRS, a gross target volume (GTV) plus planning target volume (PTV) were delineated. For FB-SRS, a GTV plus an internal target volume (ITV) and PTV were defined. Accounting for the maximal GTV diameters, a modified GTV (GTV-IORT) was expanded circumferentially to simulate a resection cavity. The best suitable round-applicator size was thereafter selected. All treatment plans were calculated homogeneously to deliver 40 Gy. Doses delivered to organs at risk (OAR) and target volumes were compared for IORT vs. both SRS modalities.
Eight patients encompassing 10 lesions were included in the study. The mean liver volume was 2,050.97 cm (SD, 650.82), and the mean GTV volume was 12.23 cm (SD, 12.62). As for target structures, GTV-IORT [19.44 cm (SD, 17.26)] were significantly smaller than both PTV DIBH-SRS [30.74 cm (SD, 24.64), p = 0.002] and PTV FB-SRS [75.82 cm (SD, 45.65), p = 0.002]. The median applicator size was 3 cm (1.5-4.5), and the mean IORT simulated delivery time was 45.45 min (SD, 19.88). All constraints were met in all modalities. Liver V showed significantly smaller volumes with IORT [63.39 cm (SD, 35.67)] when compared to DIBH-SRS [150.12 cm (SD, 81.43), p = 0.002] or FB-SRS [306.13 cm (SD, 128.75), p = 0.002]. No other statistical or dosimetrically relevant difference was observed for stomach, spinal cord, or biliary tract. Mean IORT D was 85.3% (SD, 6.05), whereas D for DIBH-SRS and FB-SRS were 99.03% (SD, 1.71; p = 0.042) and 98.04% (SD, 3.46; p = 0.036), respectively.
Kilovoltage IORT bears the potential as novel add-on treatment for resectable liver metastases, significantly reducing healthy liver exposure to radiation in comparison to SRS. Prospective clinical evidence is required to confirm this hypothesis.
目的/目标：对千伏术中放疗（IORT）和立体定向放射外科治疗（SRS）进行剂量学比较，模拟深吸气屏气（DIBH）和自由呼吸（FB）模式用于肝转移患者。
方法/材料：回顾性筛查并随机选择携带一个或两个直径<4 cm且接受手术的患者的诊断性计算机断层扫描（CT）用于本研究。对于DIBH-SRS，勾画大体肿瘤体积（GTV）加计划靶体积（PTV）。对于FB-SRS，定义GTV加内部靶体积（ITV）和PTV。根据最大GTV直径，将改良的GTV（GTV-IORT）沿圆周扩展以模拟切除腔。此后选择最合适的圆形施源器尺寸。所有治疗计划均匀计算以给予40 Gy。比较IORT与两种SRS模式下危及器官（OAR）和靶体积所接受的剂量。
本研究纳入了8例患者共10个病灶。肝脏平均体积为2050.97 cm³（标准差，650.82），GTV平均体积为12.23 cm³（标准差，12.62）。至于靶区结构，GTV-IORT[19.44 cm³（标准差，17.26）]显著小于PTV DIBH-SRS[30.74 cm³（标准差，24.64），p = 0.002]和PTV FB-SRS[75.82 cm³（标准差，45.65），p = 0.002]。施源器尺寸中位数为3 cm（1.5 - 4.5），IORT模拟照射时间平均为45.45分钟（标准差，19.88）。所有模式均满足所有限制条件。与DIBH-SRS[150.12 cm³（标准差，81.43），p = 0.002]或FB-SRS[306.13 cm³（标准差，128.75），p = 0.002]相比，IORT时肝脏V显示出显著更小的体积。对于胃、脊髓或胆道，未观察到其他统计学或剂量学相关差异。IORT的平均D为85.3%（标准差，6.05），而DIBH-SRS和FB-SRS的D分别为99.03%（标准差，1.71；p = 0.042）和98.04%（标准差，3.46；p = 0.036）。
千伏IORT作为可切除肝转移瘤的新型附加治疗具有潜力，与SRS相比，可显著减少健康肝脏的辐射暴露。需要前瞻性临床证据来证实这一假设。
