Palm Asa, Johansson Karl-Axel
Department of Therapeutic Radiation Physics, Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Göteborg, Sweden.
Acta Oncol. 2007;46(4):462-73. doi: 10.1080/02841860701218626.
The use of untraditional treatment modalities for external beam radiotherapy such as intensity modulated radiation therapy (IMRT) and proton beam therapy is increasing. This review focuses on the changes in the dose distribution and the impact on radiation related risks for long-term cancer survivors. We compare conventional radiotherapy, IMRT, and proton beam therapy based on published treatment planning studies as well as published measurements and Monte Carlo simulations of out-of-field dose distributions. Physical dose parameters describing the dose distribution in the target volume, the conformity index, the dose distribution in organs at risk, and the dose distribution in non-target tissue, respectively, are extracted from the treatment planning studies. Measured out-of-field dose distributions are presented as the dose equivalent as a function of distance from the treatment field. Data in the literature clearly shows that, compared with conventional radiotherapy, IMRT improves the dose distribution in the target volume, which may increase the probability of tumor control. IMRT also seems to increase the out-of-field dose distribution, as well as the irradiated non-target volume, although the data is not consistent, leading to a potentially increased risk of radiation induced secondary malignancies, while decreasing the dose to normal tissues close to the target volume, reducing the normal tissue complication probability. Protons show no or only minor advantage on the dose distribution in the target volume and the conformity index compared to IMRT. However, the data consistently shows that proton beam therapy substantially decreases the OAR average dose compared to the other two techniques. It is also clear that protons provide an improved dose distribution in non-target tissues compared to conventional radiotherapy and IMRT. IMRT and proton beam therapy may significantly improve tumor control for cancer patients and quality of life for long-term cancer survivors.
调强放射治疗（IMRT）和质子束治疗等非传统外照射放疗方式的使用正在增加。本综述重点关注剂量分布的变化以及对长期癌症幸存者辐射相关风险的影响。我们根据已发表的治疗计划研究以及已发表的野外剂量分布测量和蒙特卡洛模拟，比较了传统放疗、IMRT和质子束治疗。分别从治疗计划研究中提取描述靶区剂量分布、适形指数、危及器官剂量分布和非靶组织剂量分布的物理剂量参数。测量的野外剂量分布表示为剂量当量与距治疗野距离的函数关系。文献数据清楚地表明，与传统放疗相比，IMRT改善了靶区的剂量分布，这可能会增加肿瘤控制的概率。IMRT似乎还会增加野外剂量分布以及受照射的非靶体积，尽管数据并不一致，这导致辐射诱发二次恶性肿瘤的风险可能增加，同时降低了靶区附近正常组织的剂量，降低了正常组织并发症概率。与IMRT相比，质子在靶区剂量分布和适形指数方面没有优势或仅有微小优势。然而，数据一致表明，与其他两种技术相比，质子束治疗显著降低了危及器官的平均剂量。同样明显的是，与传统放疗和IMRT相比，质子在非靶组织中提供了更好的剂量分布。IMRT和质子束治疗可能会显著提高癌症患者的肿瘤控制率以及长期癌症幸存者的生活质量。
