The purpose of this study was to investigate the oxygen enhancement ratio (OER) effects on treatment planning for a hypoxic prostate tumor with proton scanning beams. Two different OER-based dose calculation models (the average model and the voxel model) were investigated by using hypoxic tumor models in this simulation study. For the hypoxic tumor model, an oxygen distribution with a range of 2.4–9.4 mmHg was used according to the clinical data. The results given by the average model and the voxel model were compared for 50% and 90% tumor control probabilities with variations in the hypoxic tumor volume and fractionation. Comparison between the treatment plans with OER-based higher predicted dose and with the conventional prescription dose was conducted to investigate the organ-at-risk (OAR) doses for the prostate case. The average model showed a higher calculated dose than the voxel model. The voxel model with a 50% control probability showed good agreement with the current prescription dose. The OER values of the average model ranged from 1.05 to 1.25, which were applied to the whole tumor volume in treatment planning. The voxel-model-based OERs were higher (1.50–1.75) than those of average model, and these OERs should be applied only for the hypoxic boost region. Regarding treatment plans, the doses of the rectum and the bladder were reduced to the tolerable range V80Gy (volume receiving equal to or greater than 80Gy) < 15% and V75Gy (volume receiving equal to or greater than 75Gy) < 15% respectively after an optimization, but the maximum dose to femoral heads was higher than 50 Gy. In conclusion, we investigated the possible ranges of the OER (1.3–1.8) for proton-beam treatment of prostate cases. A dose escalation of up to about 1.8 times can be applied for the small hypoxic region. This result, which was obtained using a model study, should be verified through clinical experiment.

中文翻译：

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增氧比效应质子治疗中前列腺治疗计划的研究

本研究的目的是通过质子扫描束研究氧增强比 (OER) 对缺氧前列腺肿瘤治疗计划的影响。在该模拟研究中使用缺氧肿瘤模型研究了两种不同的基于 OER 的剂量计算模型（平均模型和体素模型）。对于缺氧肿瘤模型，根据临床数据使用范围为 2.4-9.4 mmHg 的氧分布。将平均模型和体素模型给出的结果比较了 50% 和 90% 的肿瘤控制概率，以及缺氧肿瘤体积和分级的变化。比较基于 OER 的较高预测剂量和常规处方剂量的治疗计划，以研究前列腺病例的器官风险 (OAR) 剂量。平均模型显示出比体素模型更高的计算剂量。控制概率为 50% 的体素模型与当前处方剂量显示出良好的一致性。平均模型的 OER 值范围为 1.05 至 1.25，适用于治疗计划中的整个肿瘤体积。基于体素模型的 OERs 高于（1.50-1.75）平均模型，并且这些 OERs 应仅应用于低氧增压区域。在治疗方案方面，直肠和膀胱的剂量分别降低到可耐受范围 V80Gy（体积接收等于或大于 80Gy）<15% 和 V75Gy（体积接收等于或大于 75Gy）<15%。优化，但对股骨头的最大剂量高于 50 Gy。总之，我们调查了 OER 的可能范围（1.3-1. 8) 用于前列腺病例的质子束治疗。对于小的缺氧区域，可以应用高达约 1.8 倍的剂量递增。这个结果是通过模型研究获得的，应该通过临床实验来验证。