Medical Physics Graduate Program, Duke University, Durham, North Carolina, USA.
Int J Radiat Oncol Biol Phys. 2013 Sep 1;87(1):209-15. doi: 10.1016/j.ijrobp.2013.05.008. Epub 2013 Jun 19.
To investigate the dosimetric effects of adaptive planning on lung stereotactic body radiation therapy (SBRT).
Forty of 66 consecutive lung SBRT patients were selected for a retrospective adaptive planning study. CBCT images acquired at each fraction were used for treatment planning. Adaptive plans were created using the same planning parameters as the original CT-based plan, with the goal to achieve comparable comformality index (CI). For each patient, 2 cumulative plans, nonadaptive plan (PNON) and adaptive plan (PADP), were generated and compared for the following organs-at-risks (OARs): cord, esophagus, chest wall, and the lungs. Dosimetric comparison was performed between PNON and PADP for all 40 patients. Correlations were evaluated between changes in dosimetric metrics induced by adaptive planning and potential impacting factors, including tumor-to-OAR distances (dT-OAR), initial internal target volume (ITV1), ITV change (ΔITV), and effective ITV diameter change (ΔdITV).
34 (85%) patients showed ITV decrease and 6 (15%) patients showed ITV increase throughout the course of lung SBRT. Percentage ITV change ranged from -59.6% to 13.0%, with a mean (±SD) of -21.0% (±21.4%). On average of all patients, PADP resulted in significantly (P=0 to .045) lower values for all dosimetric metrics. ΔdITV/dT-OAR was found to correlate with changes in dose to 5 cc (ΔD5cc) of esophagus (r=0.61) and dose to 30 cc (ΔD30cc) of chest wall (r=0.81). Stronger correlations between ΔdITV/dT-OAR and ΔD30cc of chest wall were discovered for peripheral (r=0.81) and central (r=0.84) tumors, respectively.
Dosimetric effects of adaptive lung SBRT planning depend upon target volume changes and tumor-to-OAR distances. Adaptive lung SBRT can potentially reduce dose to adjacent OARs if patients present large tumor volume shrinkage during the treatment.
研究自适应计划对肺部立体定向体部放射治疗（SBRT）的剂量学影响。
选择 66 例连续肺部 SBRT 患者中的 40 例进行回顾性自适应计划研究。在每个分次采集的 CBCT 图像用于治疗计划。使用与原始 CT 计划相同的计划参数创建自适应计划，目标是实现可比的适形指数（CI）。对于每个患者，生成 2 个累积计划，非自适应计划（PNON）和自适应计划（PADP），并比较以下危及器官（OAR）：脊髓、食管、胸壁和肺。对所有 40 例患者的 PNON 和 PADP 进行剂量学比较。评估了自适应计划引起的剂量学指标变化与潜在影响因素之间的相关性，包括肿瘤与 OAR 之间的距离（dT-OAR）、初始内部靶区（ITV1）、ITV 变化（ΔITV）和有效 ITV 直径变化（ΔdITV）。
34 例（85%）患者在肺部 SBRT 过程中显示 ITV 减小，6 例（15%）患者显示 ITV 增大。ITV 变化范围从-59.6%到 13.0%，平均（±SD）为-21.0%（±21.4%）。在所有患者中，PADP 导致所有剂量学指标的平均值显著降低（P=0 至.045）。发现 ΔdITV/dT-OAR 与食管 5cc（ΔD5cc）和胸壁 30cc（ΔD30cc）剂量的变化相关（r=0.61）。对于外周（r=0.81）和中央（r=0.84）肿瘤，分别发现 ΔdITV/dT-OAR 与胸壁 ΔD30cc 之间的相关性更强。
自适应肺部 SBRT 计划的剂量学影响取决于靶区变化和肿瘤与 OAR 之间的距离。如果患者在治疗过程中表现出较大的肿瘤体积缩小，自适应肺部 SBRT 可能会降低相邻 OAR 的剂量。
