Antonovic Laura, Dasu Alexandru, Furusawa Yoshiya, Toma-Dasu Iuliana
Medical Radiation Physics, Department of Physics, Stockholm University, Stockholm, Sweden.
Department of Radiation Physics and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
J Radiat Res. 2015 Jul;56(4):639-45. doi: 10.1093/jrr/rrv016. Epub 2015 Apr 8.
Comparison of the efficiency of photon and carbon ion radiotherapy (RT) administered with the same number of fractions might be of limited clinical interest, since a wide range of fractionation patterns are used clinically today. Due to advanced photon treatment techniques, hypofractionation is becoming increasingly accepted for prostate and lung tumours, whereas patients with head and neck tumours still benefit from hyperfractionated treatments. In general, the number of fractions is considerably lower in carbon ion RT. A clinically relevant comparison would be between fractionation schedules that are optimal within each treatment modality category. In this in silico study, the relative clinical effectiveness (RCE) of carbon ions was investigated for human salivary gland tumours, assuming various radiation sensitivities related to their oxygenation. The results indicate that, for hypoxic tumours in the absence of reoxygenation, the RCE (defined as the ratio of D(50) for photons to carbon ions) ranges from 3.5 to 5.7, corresponding to carbon ion treatments given in 36 and 3 fractions, respectively, and 30 fractions for photons. Assuming that interfraction local oxygenation changes take place, results for RCE are lower than that for an oxic tumour if only a few fractions of carbon ions are used. If the carbon ion treatment is given in more than 12 fractions, the RCE is larger for the hypoxic than for the well-oxygenated tumour. In conclusion, this study showed that in silico modelling enables the study of a wide range of factors in the clinical considerations and could be an important step towards individualisation of RT treatments.
在临床实践中，如今使用的分割模式多种多样，因此比较相同分割次数下光子放疗和碳离子放疗（RT）的效率可能在临床上意义有限。由于先进的光子治疗技术，大分割放疗在前列腺癌和肺癌治疗中越来越被接受，而头颈部肿瘤患者仍受益于超分割治疗。一般来说，碳离子放疗的分割次数要少得多。临床相关的比较应该是在每种治疗方式类别中最优的分割方案之间进行。在这项计算机模拟研究中，针对人类唾液腺肿瘤，假设与氧合相关的各种辐射敏感性，研究了碳离子的相对临床疗效（RCE）。结果表明，对于无再氧合的乏氧肿瘤，RCE（定义为光子与碳离子的D(50)之比）范围为3.5至5.7，分别对应于碳离子治疗36次和3次，光子治疗30次。假设分次间局部氧合发生变化，如果仅使用少数几次碳离子治疗，RCE结果低于有氧肿瘤。如果碳离子治疗次数超过12次，乏氧肿瘤的RCE大于氧合良好的肿瘤。总之，这项研究表明，计算机模拟建模能够在临床考量中研究多种因素，可能是迈向放疗个体化的重要一步。
