Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway.
Acta Oncol. 2022 Feb;61(2):215-222. doi: 10.1080/0284186X.2021.1979248. Epub 2021 Sep 17.
Temporal lobe necrosis (TLN) is a potential late effect after radiotherapy for skull base head and neck cancer (HNC). Several photon-derived dose constraints and normal tissue complication probability (NTCP) models have been proposed, however variation in relative biological effectiveness (RBE) may challenge the applicability of these dose constraints and models in proton therapy. The purpose of this study was therefore to investigate the influence of RBE variations on risk estimates of TLN after Intensity-Modulated Proton Therapy for HNC.
Seventy-five temporal lobes from 45 previously treated patients were included in the analysis. Sixteen temporal lobes had radiation associated Magnetic Resonance image changes (TLIC) suspected to be early signs of TLN. Fixed (RWD) and variable RBE-weighed doses (RWD) were calculated using RBE = 1.1 and two RBE models, respectively. RWD and RWD for temporal lobes were compared using Friedman's test. Based on RWD, six NTCP models were fitted and internally validated through bootstrapping. Estimated probabilities from RWD and RWD were compared using paired Wilcoxon test. Seven dose constraints were evaluated separately for RWD and RWD by calculating the observed proportion of TLIC in temporal lobes meeting the specific dose constraints.
RWD were significantly higher than RWD ( < 0.01). NTCP model performance was good (AUC:0.79-0.84). The median difference in estimated probability between RWD and RWD ranged between 5.3% and 20.0% points ( < 0.01), with V and D at the smallest and largest differences, respectively. The proportion of TLIC was higher for RWD (4.0%-13.1%) versus RWD (1.3%-5.3%). For V ≤ 0.03 cc the proportion of TLIC was less than 5% for both RWD and RWD
NTCP estimates were significantly influenced by RBE variations. D as model predictor resulted in the largest deviations in risk estimates between RWD and RWD. V ≤ 0.03 cc was the most consistent dose constraint for RWD and RWD
颞叶坏死（TLN）是颅底头颈部癌症（HNC）放疗后的潜在晚期效应。已经提出了几种光子衍生剂量限制和正常组织并发症概率（NTCP）模型，但是相对生物效应（RBE）的变化可能会挑战这些剂量限制和模型在质子治疗中的适用性。因此，本研究的目的是研究 RBE 变化对 HNC 调强质子治疗后 TLN 风险估计的影响。
纳入了 45 例先前接受治疗的患者的 75 个颞叶。16 个颞叶出现与放射相关的磁共振图像变化（TLIC），疑似为 TLN 的早期迹象。分别使用 RBE = 1.1 和两种 RBE 模型计算固定（RWD）和可变 RBE 加权剂量（RWD）。使用 Friedman 检验比较 RWD 和 RWD 之间的差异。基于 RWD，拟合了六个 NTCP 模型，并通过自举法进行内部验证。使用配对 Wilcoxon 检验比较 RWD 和 RWD 估计的概率。分别使用 RWD 和 RWD 评估了七个剂量限制，计算特定剂量限制下符合 TLIC 的颞叶比例。
RWD 明显高于 RWD（<0.01）。NTCP 模型性能良好（AUC：0.79-0.84）。RWD 和 RWD 之间估计概率的中位数差异在 5.3%到 20.0%之间（<0.01），V 和 D 的差异最小和最大。RWD 的 TLIC 比例（4.0%-13.1%）高于 RWD（1.3%-5.3%）。对于 V ≤ 0.03 cc，RWD 和 RWD 的 TLIC 比例均小于 5%
RBE 变化显著影响 NTCP 估计。V 作为模型预测因子导致 RWD 和 RWD 之间风险估计的最大偏差。对于 V ≤ 0.03 cc，RWD 和 RWD 是最一致的剂量限制。
