Department of Physics - Medical Radiation Physics, Stockholm University, Stockholm, Sweden; Department of Physics, Universidade Eduardo Mondlane, Maputo, Mozambique.
Department of Oncology and Pathology, Karolinska University Hospital, Stockholm, Sweden.
Phys Med. 2017 Oct;42:263-270. doi: 10.1016/j.ejmp.2017.03.019. Epub 2017 Mar 31.
The potential of proton therapy to improve the sparing of the healthy tissue has been demonstrated in several studies. However, even small doses delivered to the organs at risk (OAR) may induce long-term detriments after radiotherapy. In this study, we investigated the possibility to reduce the risk of radiation-induced secondary cancers with intensity modulated proton therapy (IMPT), when used for radiosurgery of liver metastases.
Ten patients, previously treated for liver metastases with photon-beam based stereotactic body radiation therapy (SBRT) were retrospectively planned for radiosurgery with IMPT. A treatment plan comparison was then performed in terms of calculated risk of radiation-induced secondary cancer. The risks were estimated using two distinct models (Dasu et al., 2005; Schneider et al., 2005, 2009). The plans were compared pairwise with a two-sided Wilcoxon signed-rank test with a significance level of 0.05.
Reduced risks for induction of fatal and other types of cancers were estimated for the IMPT plans (p<0.05) with the Dasu et al.
Using the Schneider et al. model, lower risks for carcinoma-induction with IMPT were estimated for the skin, lungs, healthy part of the liver, esophagus and the remaining part of the body (p<0.05). The risk of observing sarcomas in the bone was also reduced with IMPT (p<0.05).
The findings of this study indicate that the risks of radiation-induced secondary cancers after radiosurgery of liver metastases may be reduced, if IMPT is used instead of photon-beam based SBRT.
质子治疗在提高健康组织的保护方面的潜力已在多项研究中得到证实。然而，即使是对危及器官（OAR）给予小剂量的照射，也可能在放射治疗后引发长期的不良影响。在这项研究中，我们探讨了在使用调强质子治疗（IMPT）对肝转移进行放射外科手术时，降低放射诱导继发性癌症风险的可能性。
回顾性地对 10 名先前接受光子束立体定向体放射治疗（SBRT）治疗肝转移的患者进行了 IMPT 放射外科治疗的计划。然后，根据计算出的放射诱导继发性癌症风险，对两种治疗计划进行了比较。使用两种不同的模型（Dasu 等人，2005 年；Schneider 等人，2005 年，2009 年）来估计风险。通过双侧 Wilcoxon 符号秩检验，将计划两两进行比较，显著性水平为 0.05。
与使用 Schneider 等人的模型相比，使用 Dasu 等人的模型，IMPT 计划可降低致命性和其他类型癌症的诱导风险（p<0.05）。
这项研究的结果表明，如果使用质子束的 IMPT 治疗代替光子束的 SBRT，那么在肝转移放射外科手术后，放射诱导的继发性癌症的风险可能会降低。
