Cho B C John, Schwarz Marco, Mijnheer Ben J, Bartelink Harry
Department of Radiotherapy, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Radiother Oncol. 2004 Mar;70(3):231-41. doi: 10.1016/j.radonc.2003.11.016.
Left-sided breast cancer patients pose a difficult clinical challenge when significant heart and contralateral breast irradiation are present, particularly with tangential uniform beams. The aims of the study are: (1) to design and evaluate a simplified intensity-modulated radiotherapy (IMRT) (SI) solution using pre-defined segments, (2) to compare the SI technique with a conformal (CN) and a full fluence IMRT (FI) approach using two sets of beam orientations, clinical (-C) and optimal (-O), and (3) to quantify the benefits of treatment technique and beam orientation.
Nine left-sided breast cancer patients with a maximum heart distance of at least 2.0 cm were planned using three different techniques and two different beam orientations. All three techniques were planned using clinical orientations (i.e. CN-C, FI-C and SI-C). Two techniques were planned using more optimal orientations (i.e. FI-O and SI-O). Dose-volume histograms and radiobiologic modelling are used for plan evaluation.
The average mean planning target volume (PTV) doses are 91.6+/-4.5, 98.4+/-6.3, 102.0+/-8.7, 100.0+/-5.9 and 103.9+/-8.3% for the CN-C, FI-C, SI-C, FI-O and SI-O plans, respectively. The average normal tissue complication probabilities for late excess cardiac mortality are 2.1+/-0.6, 0.2+/-0.1, 0.2+/-0.1, 0.1+/-0.0 and 0.1+/-0.0%, respectively. For a given beam orientation, FI plans are the best and CN plans are the worst. The dose distributions for the SI-C and FI-C plans are almost identical with significant heart sparing but at a cost of some target underdosage. The dose distributions are better conformed around the PTV with more optimal beam orientations, resulting in better sparing of adjacent organs at risk. FI-C plans are inferior to SI-O plans.
For clinical uniform two-beam orientations, significant heart sparing is possible with the addition of intensity modulation but at the expense of worsening target coverage. Simplified IMRT can, for all intents, be substituted for full IMRT with clinical beam orientations. Applying more optimal non-uniform beam orientations improves PTV coverage while maintaining significant heart sparing but increases the PTV dose heterogeneity.
当存在显著的心脏和对侧乳腺照射时，尤其是采用切线均匀射束时，左侧乳腺癌患者面临着困难的临床挑战。本研究的目的是：（1）设计并评估一种使用预定义射野的简化调强放疗（IMRT）（SI）方案；（2）使用两组射束方向，即临床（-C）和最佳（-O）方向，将SI技术与适形放疗（CN）和全通量IMRT（FI）方法进行比较；（3）量化治疗技术和射束方向的益处。
对9例最大心脏距离至少为2.0 cm的左侧乳腺癌患者采用三种不同技术和两种不同射束方向进行治疗计划。所有三种技术均采用临床方向进行计划制定（即CN-C、FI-C和SI-C）。两种技术采用更优化的方向进行计划制定（即FI-O和SI-O）。使用剂量体积直方图和放射生物学模型进行计划评估。
CN-C、FI-C、SI-C、FI-O和SI-O计划的平均计划靶体积（PTV）平均剂量分别为91.6±4.5%、98.4±6.3%、102.0±8.7%、100.0±5.9%和103.9±8.3%。晚期心脏额外死亡率的平均正常组织并发症概率分别为2.1±0.6%、0.2±0.1%、0.2±0.1%、0.1±0.0%和0.1±0.0%。对于给定的射束方向，FI计划最佳，CN计划最差。SI-C和FI-C计划的剂量分布几乎相同，对心脏有显著的保护作用，但代价是靶区有一定程度的剂量不足。采用更优化的射束方向时，剂量分布在PTV周围更符合要求，从而更好地保护了相邻的危险器官。FI-C计划不如SI-O计划。
对于临床均匀的双射束方向，增加调强可以显著保护心脏，但代价是靶区覆盖变差。实际上，简化IMRT可以替代临床射束方向的全IMRT。采用更优化的非均匀射束方向可改善PTV覆盖，同时保持对心脏的显著保护，但会增加PTV剂量的不均匀性。
