Rieber J, Tonndorf-Martini E, Schramm O, Rhein B, Stefanowicz S, Kappes J, Hoffmann H, Lindel K, Debus J, Rieken S
Department of Radiation Oncology, University Hospital Heidelberg, INF 400, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.
Heidelberg Institute of Radiation Oncology, Heidelberg, Germany.
Strahlenther Onkol. 2016 Nov;192(11):789-796. doi: 10.1007/s00066-016-1012-x. Epub 2016 Jul 4.
Radiosurgical treatment of brain metastases is well established in daily clinical routine. Utilization of flattening-filter-free beams (FFF) may allow for more rapid delivery of treatment doses and improve clinical comfort. Hence, we compared plan quality and efficiency of radiosurgery in FFF mode to FF techniques.
Between November 2014 and June 2015, 21 consecutive patients with 25 brain metastases were treated with stereotactic radiosurgery (SRS) in FFF mode. Brain metastases received dose-fractionation schedules of 1 × 20 Gy or 1 × 18 Gy, delivered to the conformally enclosing 80 % isodose. Three patients with critically localized or large (>3 cm) brain metastases were treated with 6 × 5 Gy. Plan quality and efficiency were evaluated by analyzing conformity, dose gradients, dose to healthy brain tissue, treatment delivery time, and number of monitor units. FFF plans were compared to those using the FF method, and early clinical outcome and toxicity were assessed.
FFF mode resulted in significant reductions in beam-on time (p < 0.001) and mean brain dose (p = 0.001) relative to FF-mode comparison plans. Furthermore, significant improvements in dose gradients and sharper dose falloffs were found for SRS in FFF mode (-1.1 %, -29.6 %; p ≤ 0.003), but conformity was slightly superior in SRS in FF mode (-1.3 %; p = 0.001). With a median follow-up time of 5.1 months, 6‑month overall survival was 63.3 %. Local control was observed in 24 of 25 brain metastases (96 %).
SRS in FFF mode is time efficient and provides similar plan quality with the opportunity of slightly reduced dose exposure to healthy brain tissue when compared to SRS in FF mode. Clinical outcomes appear promising and show only modest treatment-related toxicity.
脑转移瘤的放射外科治疗在日常临床实践中已得到广泛应用。使用无均整器射线束（FFF）可实现更快的治疗剂量交付，并提高临床舒适度。因此，我们比较了FFF模式与常规均整器（FF）技术在放射外科治疗中的计划质量和效率。
2014年11月至2015年6月期间，连续21例患有25个脑转移瘤的患者接受了FFF模式的立体定向放射外科治疗（SRS）。脑转移瘤接受了1×20 Gy或1×18 Gy的剂量分割方案，剂量分布至适形包绕的80%等剂量线。3例脑转移瘤位置关键或较大（>3 cm）的患者接受了6×5 Gy的治疗。通过分析适形度、剂量梯度、健康脑组织剂量、治疗交付时间和监测单位数量来评估计划质量和效率。将FFF计划与使用FF方法的计划进行比较，并评估早期临床结果和毒性。
与FF模式的对照计划相比，FFF模式显著缩短了照射时间（p < 0.001）并降低了平均脑剂量（p = 0.001）。此外，FFF模式下的SRS在剂量梯度和剂量下降方面有显著改善（-1.1%，-29.6%；p≤0.003），但FF模式下的SRS在适形度方面略优（-1.3%；p = 0.001）。中位随访时间为5.1个月，6个月总生存率为63.3%。25个脑转移瘤中有24个（96%）实现了局部控制。
与FF模式的SRS相比，FFF模式的SRS治疗效率高，计划质量相似，且有机会略微减少对健康脑组织的剂量暴露。临床结果显示前景良好，且治疗相关毒性较小。
