The purpose of this study was to estimate the biological impact of dosimetric perturbations of a fiducial marker and the daily number of fields in proton therapy for prostate cancer. Using a linear-quadratic model, normalized total doses (NTDs) of points where deposited dose was reduced from the prescribed dose by dosimetric perturbation of a fiducial marker were calculated in two hypothetical prostate cancer treatment schedules: a) irradiation of both parallel-opposed lateral fields and b) irradiation of alternate field in each daily treatment. The impact of hypofractionation and sublethal damage repair between irradiation on NTD was also estimated. The NTD of two fields/day schedule becomes lower than that of one field/day schedule. The difference becomes larger as dose reduction from one of two fields becomes more enhanced. The NTD reduction from the total dose in the two fields/day schedule is largest (30% of total dose) where the dose from one beam is completely lost by a fiducial marker. In contrast, the NTD reduction from the total dose in the one field/day schedule is largest (9% of total dose) where the half dose from one beam is decreased by a fiducial marker. In addition, the NTD reduction becomes larger as the fractional dose increases in a hypofractionated regimen, and when the effect of sublethal damage repair was incorporated. These influences become significant in prostate cancer since the radiobiological sensitivity α/β of prostate cancer is lower than other cancer types and normal tissues late complication. Treating with one alternate field in a daily treatment can improve a deteriorating treatment effect by dosimetric distortion of a fiducial marker in prostate cancer treatment. However, the choice of the number of beams in a fraction must also be determined by considering the sparing of normal tissues and patient-specific status.

本研究的目的是评估基准标记的剂量学扰动的生物学影响以及质子治疗前列腺癌的每日视野数。使用线性二次模型，在两个假设的前列腺癌治疗方案中计算了通过基准标记的剂量学扰动从规定剂量减少沉积剂量的点的归一化总剂量 (NTD)：a)场和 b) 在每个日常处理中交替场的辐照。还估计了照射之间的大分割和亚致死损伤修复对 NTD 的影响。两场/天计划的 NTD 变得低于一个场/天计划的 NTD。随着来自两个场之一的剂量减少变得更加增强，差异变得更大。两个射野/天计划中总剂量的 NTD 减少最大（总剂量的 30%），其中一个射束的剂量完全被基准标记物丢失。相比之下，一个射野/天计划中总剂量的 NTD 减少最大（总剂量的 9%），其中一个射束的一半剂量通过基准标记减少。此外，在大分割方案中，随着分次剂量的增加，以及当纳入亚致死损伤修复的效果时，NTD 的减少会变得更大。由于放射生物学敏感性，这些影响在前列腺癌中变得显着 一个射野/天计划中总剂量的 NTD 减少最大（总剂量的 9%），其中一个射束的一半剂量通过基准标记减少。此外，在大分割方案中，随着分次剂量的增加，以及当纳入亚致死损伤修复的效果时，NTD 的减少会变得更大。由于放射生物学敏感性，这些影响在前列腺癌中变得显着 一个射野/天计划中总剂量的 NTD 减少最大（总剂量的 9%），其中一个射束的一半剂量通过基准标记减少。此外，在大分割方案中，随着分次剂量的增加，以及当纳入亚致死损伤修复的效果时，NTD 的减少会变得更大。由于放射生物学敏感性，这些影响在前列腺癌中变得显着前列腺癌的α / β低于其他癌症类型和正常组织的晚期并发症。在日常治疗中用一个替代场进行治疗可以通过前列腺癌治疗中基准标记的剂量学失真来改善恶化的治疗效果。然而，部分中光束数量的选择也必须通过考虑正常组织的保留和患者特定状态来确定。