Mohiuddin Majid M, Nichols Elizabeth M, Marter Kimberley J, Flannery Todd W
Northwest Radiation Oncology & Division of Oncology, UT Medical School at Houston, Houston, TX, USA.
Med Dosim. 2012 Autumn;37(3):339-43. doi: 10.1016/j.meddos.2011.11.008. Epub 2012 Feb 4.
To determine whether small field boost (SFB) replanning is necessary when the lumpectomy cavity (LPC) decreases during whole-breast irradiation (WBI) and what parameters might predict a change in the SFB plan. Forty patients had computed tomography (CT) simulation (CT1) within 60 days of surgery and were resimulated (CT2) after 37.8-41.4 Gy for SFB planning. A 3-field photon plan and a single en face electron plan were created on both CTs and compared. In the 26 patients who had a ≥5 cm(3) and a ≥25% decrease in lumpectomy cavity volume (LCV) between CT scans, the SFB plan using photons was different in terms of normal breast tissue volume irradiated (BTV) (p < 0.001), and field dimensions (p < 0.001). In 20/35 patients, the energy or field size changed for electron plans on CT2, but no tested characteristics predicted for a change. Less BTV was irradiated using electrons than photons in 29% (CT1) to 37% (CT2). SFB replanning needs to be individualized to each patient because of the variety of factors that can impact dosimetric planning. Replanning is recommended when using 3-field photons if the patient has experienced a ≥5 cm(3) and a ≥25% decrease in LCV during WBI. Some patients may benefit from electron SFB replanning but no tested characteristics reliably predict those who may benefit the most. The amount of BTV irradiated is less with electrons than in photon plans and this has the potential to improve cosmesis, a clinically important outcome in breast-conserving therapy.
确定在全乳照射（WBI）期间乳房切除腔（LPC）缩小时小野加量（SFB）重新计划是否必要，以及哪些参数可能预测SFB计划的变化。40例患者在手术60天内进行了计算机断层扫描（CT）模拟（CT1），并在37.8 - 41.4 Gy后进行重新模拟（CT2）以进行SFB计划。在两个CT上均创建了一个3野光子计划和一个单野正面电子计划并进行比较。在CT扫描之间乳房切除腔体积（LCV）减少≥5 cm³且≥25%的26例患者中，使用光子的SFB计划在正常乳腺组织受照体积（BTV）方面不同（p < 0.001），且野尺寸也不同（p < 0.001）。在35例患者中的20例中，CT2上电子计划的能量或野大小发生了变化，但没有测试特征可预测这种变化。在29%（CT1）至37%（CT2）的患者中，电子计划照射的BTV比光子计划少。由于多种因素会影响剂量计划，SFB重新计划需要针对每个患者进行个体化。如果患者在WBI期间LCV减少≥5 cm³且≥25%，使用3野光子时建议重新计划。一些患者可能从电子SFB重新计划中获益，但没有测试特征能可靠地预测哪些患者获益最大。电子计划照射的BTV量比光子计划少，这有可能改善美容效果，而美容效果是保乳治疗中一个重要的临床结果。
