Wang Lei, Mohajer Jonathan, McNair Helen, Harris Emma, Lalondrelle Susan
The Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.
Adv Radiat Oncol. 2024 Jul 1;9(9):101560. doi: 10.1016/j.adro.2024.101560. eCollection 2024 Sep.
Owing to substantial interfraction motion in cervical cancer, plan-of-the-day (PotD) adaptive radiation therapy may be of benefit to patients. Implementation is limited by uncertainty over how to generate the planning target volumes (PTVs). We compared published methods on our own patients.
Forty patients each had 3 planning scans with variable bladder filling and daily cone beam computed tomographies (cone beam CTs) during radiation therapy; 5 to 11 cone beam CTs were selected to represent interfraction motion. Clinical target volumes (CTVs) and organs at risk were contoured following EMBRACE-II guidelines. A literature search identified 30 adaptive and nonadaptive solutions to PTV generation, which we applied to our patients. PTV sizes and mean coverage of the daily CTV were determined. For 11 patients, the clinically implemented, subjectively edited plan library was also investigated.
Eleven studies assessed 15 PotD strategies against nonadaptive comparators on a median of 14 patients (range, 9-23). Some PotD approaches applied margin recipes to the CTV on each planning scan, some modeled the CTV against bladder volume, and others applied incremental isotropic margins to the CTV with a single planning scan. Generally, coverage improved as PTV size increased. The fixed isotropic margin required to provide 100% coverage of all patients was 44 mm, with a mean PTV size of 3316 cm. The PotD strategy with the best coverage was a 2-plan library formed by modeling the CTV against bladder volume with extrapolation; it provided 98% mean coverage with 1419-cm mean PTV size. A 3-plan library consisting of the CTV on each planning scan with 10-mm margin provided 96% mean coverage with 1346-cm mean PTV size. The clinically implemented solution that employed subjective extrapolation had mean 100% coverage and 1282-cm PTV size on the 11-patient subset. Coverage provided by the best nonadaptive strategies was not statistically superior to the best PotD strategy ( = .13), but PTVs were larger ( = .02).
We identified a modeled 2-plan method and a simple 3-plan method, both of which provided excellent coverage with small PTVs compared with nonadaptive strategies.
由于宫颈癌存在显著的分次间运动，当日计划（PotD）自适应放射治疗可能对患者有益。其实施受到如何生成计划靶区（PTV）的不确定性的限制。我们在自己的患者身上比较了已发表的方法。
40例患者在放疗期间均进行了3次不同膀胱充盈状态的计划扫描以及每日锥形束计算机断层扫描（锥形束CT）；选择5至11次锥形束CT来代表分次间运动。按照EMBRACE-II指南勾勒临床靶区（CTV）和危及器官。文献检索确定了30种生成PTV的自适应和非自适应方案，并应用于我们的患者。确定了PTV大小和每日CTV的平均覆盖情况。对于11例患者，还研究了临床实施的、经主观编辑的计划库。
11项研究在中位数为14例患者（范围9 - 23例）中评估了15种PotD策略与非自适应对照方法。一些PotD方法在每次计划扫描时将边界处方应用于CTV，一些根据膀胱体积对CTV进行建模，还有一些在单次计划扫描时对CTV应用递增的各向同性边界。一般来说，随着PTV大小增加，覆盖情况有所改善。为所有患者提供100%覆盖所需的固定各向同性边界为44 mm，平均PTV大小为3316 cm。覆盖情况最佳的PotD策略是通过根据膀胱体积对CTV进行建模并外推形成的双计划库；其平均覆盖为98%，平均PTV大小为1419 cm。由每次计划扫描时带有10 mm边界的CTV组成的三计划库，平均覆盖为96%，平均PTV大小为1346 cm。在11例患者的子集中，采用主观外推的临床实施方案平均覆盖为100%，PTV大小为1282 cm。最佳非自适应策略提供的覆盖在统计学上并不优于最佳PotD策略（P = 0.13），但PTV更大（P = 0.02）。
我们确定了一种建模的双计划方法和一种简单的三计划方法，与非自适应策略相比，这两种方法均能以较小的PTV提供出色的覆盖。
