Hedrick Samantha G, Buchanan Laura, Mahan Stephen, Ramsey Chester
Thompson Proton Center, Knoxville, TN 37909, USA.
Int J Part Ther. 2024 Aug 28;13:100628. doi: 10.1016/j.ijpt.2024.100628. eCollection 2024 Sep.
The purpose of this work was to reduce the severity of radiation dermatitis for breast cancer patients receiving pencil beam scanning proton therapy. The hypothesis was that eliminating proton spots (SpotDelete) in the 0.5 cm skin rind would reduce the potentially higher relative biological effectiveness (RBE) known to occur at the Bragg Peak.
Our center has been using an in-house developed Python script in RayStation since 2021 to remove spots from the skin rind of breast patients. In this work, we retrospectively reviewed the on-treatment visit data from a cohort of breast patients treated with hypofractionation (16 fractions) before this technique (MinDepth) and after (SpotDelete) to acquire the physician-reported radiation dermatitis scores. We evaluated the delivered treatment plans, calculating the linear energy transfer (LET) and applying 3 variable RBE models, Carabe-Fernandez, Wedenberg, and McNamara. An α/β of 10 was assumed for the skin.
In the MinDepth cohort ( = 28), grade 1, 2, and 3 dermatitis accounted for 57%, 36%, and 7% of the cases, respectively. For SpotDelete ( = 27), the incidence rate of grade 1 and 2 acute radiation dermatitis was 67% and 37%, respectively. There were 0 instances of grade 3 dermatitis observed in the SpotDelete cohort. The onset of radiation dermatitis in the SpotDelete cohort was delayed compared to MinDepth, occurring 1 week later in the course of treatment. There was no significant difference in LET or in any of the variable RBE models when analyzing the 0.5 cm skin rind between the cohorts.
Despite the lack of correlation in LET or RBE, SpotDelete has been shown to reduce the severity and onset of radiation dermatitis. Possibly, more research into the α/β for skin and RBE models based on skin cell lines could provide insight into the efficacy of the SpotDelete technique.
本研究旨在降低接受笔形束扫描质子治疗的乳腺癌患者放射性皮炎的严重程度。假设是消除皮肤表层0.5厘米范围内的质子束斑（SpotDelete）可降低已知在布拉格峰处出现的潜在更高相对生物效应（RBE）。
自2021年以来，我们中心一直在RayStation中使用自行开发的Python脚本，以去除乳腺癌患者皮肤表层的束斑。在本研究中，我们回顾性分析了一组采用大分割（16次分割）治疗的乳腺癌患者在该技术应用前（最小深度）和应用后（SpotDelete）的治疗期间就诊数据，以获取医生报告的放射性皮炎评分。我们评估了所实施的治疗计划，计算了线能量传递（LET）并应用了3种可变RBE模型，即卡拉贝 - 费尔南德斯模型、韦登伯格模型和麦克纳马拉模型。假设皮肤的α/β值为10。
在最小深度组（n = 28）中，1级、2级和3级皮炎分别占病例的57%、36%和7%。对于SpotDelete组（n = 27），1级和2级急性放射性皮炎的发生率分别为67%和37%。在SpotDelete组中未观察到3级皮炎病例。与最小深度组相比，SpotDelete组放射性皮炎的发作有所延迟，在治疗过程中晚1周出现。在分析两组之间的0.5厘米皮肤表层时，LET或任何可变RBE模型均无显著差异。
尽管LET或RBE之间缺乏相关性，但SpotDelete已被证明可降低放射性皮炎的严重程度和发作时间。可能，对皮肤的α/β值以及基于皮肤细胞系的RBE模型进行更多研究，可为SpotDelete技术的疗效提供深入了解。
