School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, WA, 6009, Australia.
Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia.
Radiat Oncol. 2024 Jan 2;19(1):1. doi: 10.1186/s13014-023-02392-4.
SBRT is an effective local treatment for patients with early-stage non-small cell lung cancer (NSCLC). This treatment is currently used in patients who have poor lung function or who decline surgery. As SBRT usually has small PTV margins, reducing the beam-on-time (BOT) is beneficial for accurate dose delivery by minimising intrafraction motion as well as improved patient comfort. Removal of the linear accelerator flattening filter can provide a higher dose rate which results in a faster treatment. In addition, the choice of photon energy can also affect the dose distribution to the target and the organs-at-risk (OAR). In this systematic review, studies analysing the choice of various photon beam energies, with a flattening filter or flattening filter free (FFF), were compared for their overall dosimetric benefit in the SBRT treatment for early-stage NSCLC. It was found that FFF treatment delivers a comparatively more conformal dose distribution, as well as a better homogeneity index and conformity index, and typically reduces BOT by between 30 and 50%. The trade-off may be a minor increase in monitor units for FFF treatment found in some studies but not others. Target conformity and OAR sparing, particularly lung doses appear better with 6MV FFF, but 10MV FFF was marginally more advantageous for skin sparing and BOT reduction. The favourable beam modality for clinical use would depend on the individual case, for which tumour size and depth, radiotherapy technique, as well as fractionation scheme need to be taken into account.
立体定向体部放疗（SBRT）是一种治疗早期非小细胞肺癌（NSCLC）的有效局部治疗方法。这种治疗方法目前用于肺功能较差或拒绝手术的患者。由于 SBRT 通常有较小的 PTV 边缘，因此减少射束开启时间（BOT）有利于通过最小化分次内运动来准确输送剂量，并提高患者舒适度。移除直线加速器的均整滤过器可以提供更高的剂量率，从而实现更快的治疗。此外，光子能量的选择也会影响靶区和危及器官（OAR）的剂量分布。在这项系统评价中，分析了选择各种光子束能量（带或不带均整滤过器）的研究，比较了它们在早期 NSCLC 的 SBRT 治疗中的整体剂量学优势。结果发现，FFF 治疗可提供更适形的剂量分布，以及更好的均匀性指数和适形性指数，并且通常可将 BOT 减少 30%至 50%。在一些研究中发现 FFF 治疗的 Monitor Units 会略有增加，但在其他研究中则没有。对于靶区适形性和 OAR 保护，6MV FFF 似乎可更好地保护肺剂量，但 10MV FFF 在皮肤保护和 BOT 减少方面略有优势。对于临床应用，有利的射束模式将取决于具体情况，需要考虑肿瘤大小和深度、放疗技术以及分割方案。
