Dickie Colleen, Parent Amy, Griffin Anthony M, Wunder Jay, Ferguson Peter, Chung Peter W, Craig Tim, Sharpe Michael, Becker Nathan, Shultz David, Catton Charles N, O'Sullivan Brian
Department of Radiation Oncology, Princess Margaret Cancer Centre, UHN, Toronto, Canada; University of Toronto, Canada.
Department of Radiation Oncology, Princess Margaret Cancer Centre, UHN, Toronto, Canada.
Radiother Oncol. 2017 Mar;122(3):458-463. doi: 10.1016/j.radonc.2016.12.028. Epub 2017 Feb 4.
To determine the value of preoperative adaptive radiotherapy (ART) for soft tissue sarcoma patients (STS) by modeling the dosimetric consequences of tumour volume changes (TVC) using different external beam radiotherapy techniques.
A subset of 22 STS patients from a recent trial (NCT00188175) underwent a repeat CT scan (CT2) prompted by TVC>1cm during IMRT; 14 tumours grew, 8 shrank. Conformal and conventional plans were modelled in addition to IMRT replicating original criteria from the initial planning dataset (CT1):95% PTV encompassed by 97% prescribed dose. CT1 RT parameters for all plans were applied to CT2 for dosimetric assessment of TVC. Co-registration of CT1 and CT2 permitted comparison of original and new contours.
Mean TVC was 45% for growing and 33% for the shrinking cohort with TVC prompting CT2 at a mean of 13 fractions. For growers, the lack of target coverage on CT2 was statistically significant but was adequate for shrinkers.
GTV expansion of >1cm during RT may result in target underdosage independent of RT technique. ART applied offline for TV increases >1cm is a practical adaptive strategy to ensure tumour coverage during RT. TV shrinkage may allow for normal tissue sparing, which should be investigated prospectively.
通过使用不同的外照射放疗技术对肿瘤体积变化（TVC）的剂量学后果进行建模，确定术前适形放疗（ART）对软组织肉瘤患者（STS）的价值。
在一项近期试验（NCT00188175）中的22例STS患者的子集，在调强放疗（IMRT）期间因TVC>1cm而接受了重复CT扫描（CT2）；14个肿瘤增大，8个肿瘤缩小。除了IMRT外，还对适形和传统计划进行了建模，复制了初始计划数据集（CT1）的原始标准：95%的计划靶体积（PTV）被97%的处方剂量所覆盖。将所有计划的CT1放疗参数应用于CT2，以进行TVC的剂量学评估。CT1和CT2的配准允许比较原始轮廓和新轮廓。
增大组的平均TVC为45%，缩小组为33%，TVC促使进行CT2扫描的平均次数为13次。对于增大的肿瘤，CT2上靶区覆盖不足具有统计学意义，但对于缩小的肿瘤则足够。
放疗期间GTV扩大>1cm可能导致靶区剂量不足，与放疗技术无关。对于TV增加>1cm离线应用ART是一种切实可行的适形策略，以确保放疗期间肿瘤得到覆盖。TV缩小可能允许 sparing正常组织，这应进行前瞻性研究。
