Department of Radiation Oncology, University Hospital Wuerzburg, Wuerzburg, Germany.
Int J Radiat Oncol Biol Phys. 2011 Nov 15;81(4):e275-82. doi: 10.1016/j.ijrobp.2011.01.067. Epub 2011 Apr 15.
To evaluate doses to the microscopic disease (MD) in adaptive radiotherapy (ART) for locally advanced non-small-cell lung cancer (NSCLC) and to model tumor control probability (TCP).
In a retrospective planning study, three-dimensional conformal treatment plans for 13 patients with locally advanced NSCLC were adapted to shape and volume changes of the gross tumor volume (GTV) once or twice during conventionally fractionated radiotherapy with total doses of 66 Gy; doses in the ART plans were escalated using an iso-mean lung dose (MLD) approach compared to non-adapted treatment. Dose distributions to the volumes of suspect MD were simulated for a scenario with synchronous shrinkage of the MD and GTV and for a scenario of a stationary MD despite GTV shrinkage; simulations were performed using deformable image registration. TCP calculations considering doses to the GTV and MD were performed using three different models.
Coverage of the MD at 50 Gy was not compromised by ART. Coverage at 60 Gy in the scenario of a stationary MD was significantly reduced from 92% ± 10% to 73% ± 19% using ART; however, the coverage was restored by iso-MLD dose escalation. Dose distributions in the MD were sufficient to achieve a TCP >80% on average in all simulation experiments, with the clonogenic cell density the major factor influencing TCP. The combined TCP for the GTV and MD was 19.9% averaged over all patients and TCP models in non-adaptive treatment with 66 Gy. Iso-MLD dose escalation achieved by ART increased the overall TCP by absolute 6% (adapting plan once) and by 8.7% (adapting plan twice) on average. Absolute TCP values were significantly different between the TCP models; however, all TCP models suggested very similar TCP increase by using ART.
Adaptation of radiotherapy to the shrinking GTV did not compromise dose coverage of volumes of suspect microscopic disease and has the potential to increase TCP by >40% compared with radiotherapy planning without ART.
评估局部晚期非小细胞肺癌（NSCLC）自适应放疗（ART）中对微观疾病（MD）的剂量，并对肿瘤控制概率（TCP）进行建模。
在一项回顾性计划研究中，对 13 例局部晚期 NSCLC 患者的三维适形治疗计划进行了调整，以便在常规分割放疗中使总剂量达到 66 Gy 时，GTV 的形状和体积发生变化，进行一次或两次调整；ART 计划中的剂量通过与未调整治疗相比使用等平均肺剂量（MLD）方法进行了升级。使用变形图像配准模拟 MD 与 GTV 同步收缩以及 GTV 收缩时 MD 静止两种情况下的 MD 体积的剂量分布；使用三个不同的模型进行了考虑 GTV 和 MD 剂量的 TCP 计算。
ART 不会影响 MD 的 50 Gy 覆盖率。在 MD 静止的情况下，ART 可将 60 Gy 时的覆盖范围从 92%±10%显著降低至 73%±19%；但是，通过等 MLD 剂量升级可以恢复覆盖范围。在所有模拟实验中，MD 中的剂量分布足以平均实现 TCP>80%，其中克隆形成细胞密度是影响 TCP 的主要因素。在所有患者和 TCP 模型中，非自适应治疗 66 Gy 时的 GTV 和 MD 的联合 TCP 平均为 19.9%。ART 实现的等 MLD 剂量升级平均使整体 TCP 增加了 6%（一次调整计划）和 8.7%（两次调整计划）。绝对 TCP 值在 TCP 模型之间存在显著差异；但是，所有 TCP 模型均表明，与没有 ART 的放疗计划相比，使用 ART 具有增加 TCP 的潜力。
将放疗调整为收缩的 GTV 不会影响可疑微观疾病体积的剂量覆盖范围，并且与没有 ART 的放疗计划相比，通过 ART 有可能将 TCP 提高>40%。
