Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
Radiother Oncol. 2020 Aug;149:49-54. doi: 10.1016/j.radonc.2020.04.057. Epub 2020 May 5.
The stomach displays large anatomical changes in size, shape and position, which implies the need for plan adaptation for gastric cancer patients who receive pre-operative radiotherapy. We evaluated the feasibility and necessity of a CBCT-guided library of plans (LoP) strategy in gastric cancer radiotherapy.
Eight gastric cancer patients treated with 24-25 fractions of single-plan radiotherapy with daily CBCT imaging were included. The target was delineated on the pre-treatment CT and first 5 CBCTs to create a patient-specific LoP. Plan selections were performed by 12 observers in a training stage (2-3 CBCTs per patient) and an assessment stage (17 CBCTs per patient). The observers were asked to select the smallest plan that encompassed the target on the CBCT. A total of 136 plan selections were evaluated in the assessment stage.
Delineations on CBCTs showed that in 90% of the 40 delineated fractions part of the CTV was outside the PTV based on the pre-treatment CT. At least two-thirds of the observers agreed on the selected plan in 65.2% and 70% of the fractions in the training stage and the assessment stage, respectively. For each patient, at least two different plans from the LoP were the most selected plan.
A CBCT-guided patient-specific LoP strategy is feasible for gastric cancer patients, yielding good agreement in plan selections. Unless generous margins are used to avoid frequent geometric misses, it is likely that part of the target will be missed with single-plan radiotherapy.
胃在大小、形状和位置上会发生较大的解剖学变化，这意味着对于接受术前放疗的胃癌患者，需要对计划进行适应性调整。我们评估了基于锥形束 CT（CBCT）的计划库（LoP）策略在胃癌放疗中的可行性和必要性。
共纳入 8 例接受 24-25 次分割、单次计划放疗并每日行 CBCT 成像的胃癌患者。在治疗前 CT 和前 5 次 CBCT 上勾画靶区，以创建患者特定的 LoP。在培训阶段（每位患者 2-3 次 CBCT）和评估阶段（每位患者 17 次 CBCT），由 12 名观察者进行计划选择。观察者被要求在 CBCT 上选择包含靶区的最小计划。在评估阶段共评估了 136 次计划选择。
CBCT 上的勾画显示，在 40 次勾画的分次中，有 90%的CTV 部分位于基于治疗前 CT 的 PTV 之外。在培训阶段和评估阶段，分别有 65.2%和 70%的分次中，至少有三分之二的观察者对所选计划达成一致。对于每位患者，LoP 中至少有两个不同的计划是最常选择的计划。
对于胃癌患者，基于 CBCT 的患者特定的 LoP 策略是可行的，在计划选择方面具有良好的一致性。除非使用较大的外放边界以避免频繁的几何学误差，否则单次计划放疗可能会导致部分靶区遗漏。
