De Santis Maria C, Nardone Luigia, Diletto Barbara, Canna Roberta, Dispinzieri Michela, Marino Lorenza, Lozza Laura, Valentini Vincenzo
1 Radiotherapy Unit 1, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
2 Department of Radiation Oncology, Catholic University of the Sacred Heart, Rome, Italy.
Br J Radiol. 2016 Oct;89(1066):20160264. doi: 10.1259/bjr.20160264. Epub 2016 Jul 25.
After breast conservative surgery (BCS) and whole-breast radiotherapy (WBRT), the use of boost irradiation is recommended especially in patients at high risk. However, the standard technique and the definition of the boost volume have not been well defined.
We retrospectively compared an anticipated pre-operative photon boost on the tumour, administered with low-dose fractionated radiotherapy, and neoadjuvant chemotherapy with two different sequential boost techniques, administered after BCS and standard adjuvant WBRT: (1) a standard photon beam (2) and an electron beam technique on the tumour bed of the same patients. The plans were analyzed for the dosimetric coverage of the CT-delineated irradiated volume. The minimal dose received by 95% of the target volume (D95), the minimal dose received by 90% of the target volume (D90) and geographic misses were evaluated.
15 patients were evaluated. The sequential photon and electron boost techniques resulted in inferior target volume coverage compared with the anticipated boost technique, with a median D95 of 96.3% (range 94.7-99.6%) and 0.8% (range 0-30%) and a median D90 of 99.1% (range 90.2-100%) and 54.7% (range 0-84.8%), respectively. We observed a geographic miss in 26.6% of sequential electron plans. The results of the anticipated boost technique were better: 99.4% (range 96.5-100%) and 97.1% (range 86.2-99%) for median D90 and median D95, respectively, and no geographic miss was observed. We observed a dose reduction to the heart, with left-sided breast irradiation, using the anticipated pre-operative boost technique, when analyzed for all dose-volume parameters. When compared with the sequential electron plans, the pre-operative photon technique showed a higher median ipsilateral lung Dmax.
Our data show that an anticipated pre-operative photon boost results in a better coverage with respect to the standard sequential boost while also saving the organs at risk and consequently fewer side effects.
This is the first dosimetric study that evaluated the association between an anticipated boost and neoadjuvant chemotherapy treatment.
在保乳手术（BCS）和全乳放疗（WBRT）后，尤其对于高危患者，推荐使用瘤床加量照射。然而，加量照射的标准技术和加量体积的定义尚未明确。
我们回顾性比较了术前对肿瘤进行的预期光子瘤床加量照射（采用低分割放疗）以及新辅助化疗，与保乳手术和标准辅助全乳放疗后采用的两种不同序贯加量技术：（1）标准光子束；（2）对同一患者瘤床采用电子束技术。分析这些计划对CT勾画的照射体积的剂量覆盖情况。评估95%靶体积接受的最小剂量（D95）、90%靶体积接受的最小剂量（D90）和几何遗漏情况。
评估了15例患者。与预期加量技术相比，序贯光子和电子加量技术导致靶体积覆盖较差，D95中位数分别为96.3%（范围94.7 - 99.6%）和0.8%（范围0 - 30%），D90中位数分别为99.1%（范围90.2 - 100%）和54.7%（范围0 - 84.8%）。我们在26.6%的序贯电子计划中观察到几何遗漏。预期加量技术的结果更好：D90中位数和D95中位数分别为99.4%（范围96.5 - 100%）和97.1%（范围86.2 - 99%），且未观察到几何遗漏。在分析所有剂量 - 体积参数时，我们发现采用预期术前加量技术对左侧乳房照射时，心脏剂量降低。与序贯电子计划相比，术前光子技术同侧肺的Dmax中位数更高。
我们的数据表明，预期术前光子加量相对于标准序贯加量能带来更好的覆盖，同时保护了危及器官，从而减少副作用。
这是第一项评估预期加量与新辅助化疗治疗之间关联的剂量学研究。
