Faught Austin M, Miyasaka Yuya, Kadoya Noriyuki, Castillo Richard, Castillo Edward, Vinogradskiy Yevgeniy, Yamamoto Tokihiro
Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Int J Radiat Oncol Biol Phys. 2017 Oct 1;99(2):325-333. doi: 10.1016/j.ijrobp.2017.04.024. Epub 2017 Apr 26.
Computed tomographic (CT) ventilation imaging is a new modality that uses 4-dimensional (4D) CT information to calculate lung ventilation. Although retrospective studies have reported on the reduction in dose to functional lung, no work to our knowledge has been published in which the dosimetric improvements have been translated to a reduction in the probability of pulmonary toxicity. Our work estimates the reduction in toxicity for CT ventilation-based functional avoidance planning.
Seventy previously treated lung cancer patients who underwent 4DCT imaging were used for the study. CT ventilation maps were calculated with 4DCT deformable image registration and a density change-based algorithm. Pneumonitis was graded on the basis of imaging and clinical presentation. Maximum likelihood methods were used to generate normal tissue complication probability (NTCP) models predicting grade 2 or higher (2+) and grade 3+ pneumonitis as a function of dose (V5 Gy, V10 Gy, V20 Gy, V30 Gy, and mean dose) to functional lung. For 30 patients a functional plan was generated with the goal of reducing dose to the functional lung while meeting Radiation Therapy Oncology Group 0617 constraints. The NTCP models were applied to the functional plans and the clinically used plans to calculate toxicity reduction.
By the use of functional avoidance planning, absolute reductions in grade 2+ NTCP of 6.3%, 7.8%, and 4.8% were achieved based on the mean fV20 Gy, fV30 Gy, and mean dose to functional lung metrics, respectively. Absolute grade 3+ NTCP reductions of 3.6%, 4.8%, and 2.4% were achieved with fV20 Gy, fV30 Gy, and mean dose to functional lung. Maximum absolute reductions of 52.3% and 16.4% were seen for grade 2+ and grade 3+ pneumonitis for individual patients.
Our study quantifies the possible toxicity reduction from CT ventilation-based functional avoidance planning. Reductions in grades 2+ and 3+ pneumonitis were 7.1% and 4.7% based on mean dose-function metrics, with reductions as high as 52.3% for individual patients. Our work provides seminal data for determining the potential toxicity benefit from incorporating CT ventilation into thoracic treatment planning.
计算机断层扫描（CT）通气成像技术是一种利用四维（4D）CT信息计算肺通气情况的新方法。尽管回顾性研究报道了对功能性肺组织剂量的降低，但据我们所知，尚未有研究发表将剂量学改进转化为肺毒性概率降低的相关内容。我们的研究旨在评估基于CT通气的功能回避计划对毒性降低的效果。
本研究纳入了70例曾接受过治疗且已进行4DCT成像的肺癌患者。通过4DCT可变形图像配准和基于密度变化的算法计算CT通气图。根据影像学表现和临床表现对肺炎进行分级。采用最大似然法生成正常组织并发症概率（NTCP）模型，预测2级或更高级别（2+）以及3级及以上肺炎作为功能性肺组织剂量（V5 Gy、V10 Gy、V20 Gy、V30 Gy和平均剂量）的函数。对30例患者制定了功能计划，目标是在满足放射治疗肿瘤学组0617标准的同时降低对功能性肺组织的剂量。将NTCP模型应用于功能计划和临床使用的计划，以计算毒性降低情况。
通过使用功能回避计划，基于平均fV20 Gy、fV30 Gy和功能性肺组织平均剂量指标，2+级NTCP的绝对降低率分别为6.3%、7.8%和4.8%。fV20 Gy、fV30 Gy和功能性肺组织平均剂量对应的3+级NTCP绝对降低率分别为3.6%、4.8%和2.4%。个别患者的2+级和3+级肺炎的最大绝对降低率分别为52.3%和16.4%。
我们的研究量化了基于CT通气的功能回避计划可能带来的毒性降低情况。基于平均剂量 - 功能指标，2+级和3+级肺炎的降低率分别为7.1%和4.7%，个别患者的降低率高达52.3%。我们的研究为确定将CT通气纳入胸部治疗计划可能带来的潜在毒性益处提供了重要数据。
