Yahyapour R, Salajegheh A, Safari A, Amini P, Rezaeyan A, Amraee A, Najafi M
School of Medicine, Jiroft University of Medical Sciences, Jiroft, Iran.
Department of Radiology, School of Paramedical, Shiraz University of Medical Sciences, Shiraz, Iran.
J Biomed Phys Eng. 2018 Dec 1;8(4):435-446. eCollection 2018 Dec.
Bystander or non-targeted effect is known to be an interesting phenomenon in radiobiology. The genetic consequences of bystander effect on non-irradiated cells have shown that this phenomenon can be considered as one of the most important factors involved in secondary cancer after exposure to ionizing radiation. Every year, millions of people around the world undergo radiotherapy in order to cure different types of cancers. The most crucial aim of radiotherapy is to improve treatment efficiency by reducing early and late effects of exposure to clinical doses of radiation. Secondary cancer induction resulted from exposure to high doses of radiation during treatment can reduce the effectiveness of this modality for cancer treatment. The perception of carcinogenesis risk of bystander effects and factors involved in this phenomenon might help reduce secondary cancer incidence years after radiotherapy. Different modalities such as radiation LET, dose and dose rate, fractionation, types of tissue, gender of patients, etc. may be involved in carcinogenesis risk of bystander effects. Therefore, selecting an appropriate treatment modality may improve cost-effectiveness of radiation therapy as well as the quality of life in survived patients. In this review, we first focus on the carcinogenesis evidence of non-targeted effects in radiotherapy and then review physical and biological factors that may influence the risk of secondary cancer induced by this phenomenon.
旁观者或非靶向效应是放射生物学中一个有趣的现象。旁观者效应对未受照射细胞的遗传影响表明，这一现象可被视为电离辐射暴露后引发继发性癌症的最重要因素之一。每年，全球数百万人接受放射治疗以治愈不同类型的癌症。放射治疗的最关键目标是通过减少临床剂量辐射暴露的早期和晚期影响来提高治疗效果。治疗期间因高剂量辐射暴露导致的继发性癌症诱发会降低这种癌症治疗方式的有效性。了解旁观者效应的致癌风险以及该现象涉及的因素可能有助于降低放射治疗多年后的继发性癌症发病率。不同的因素，如辐射传能线密度（LET）、剂量和剂量率、分次照射、组织类型、患者性别等，可能与旁观者效应的致癌风险有关。因此，选择合适的治疗方式可能会提高放射治疗的成本效益以及存活患者的生活质量。在本综述中，我们首先关注放射治疗中非靶向效应的致癌证据，然后回顾可能影响这一现象诱发继发性癌症风险的物理和生物学因素。
