BACKGROUND To investigate the role of intensity-modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT), realised with RapidArc and RapidPlan methods (RA_RP) for neoadjuvant radiotherapy in locally advanced oesophagal cancer. METHODS Twenty patients were retrospectively planned for IMPT (with two fields, (IMPT_2F) or with three fields (IMPT_3F)) and RA_RP and the results were compared according to dose-volume metrics. Estimates of the excess absolute risk (EAR) of secondary cancer induction were determined for the lungs. For the cardiac structures, the relative risk (RR) of coronary artery disease (CAD) and chronic heart failure (CHF) were estimated. RESULTS Both the RA_RP and IMPT approached allowed to achieve the required coverage for the gross tumour volume, (GTV) and the clinical and the planning target volumes, CTV and PTV (V98% > 98 for CTV and GTV and V95% > 95 for the PTV)). The conformity index resulted in 0.88 ± 0.01, 0.89 ± 0.02 and 0.89 ± 0.02 for RA_RP, IMPT_2F and IMPT_3F respectively. With the same order, the homogeneity index for the PTV resulted in 5.6 ± 0.6%, 4.4 ± 0.9% and 4.5 ± 0.8%. Concerning the organs at risk, the IMPT plans showed a systematic and statistically significant incremental sparing when compared to RA_RP, especially for the heart. The mean dose to the combined lungs was 8.6 ± 2.9 Gy for RA_RP, 3.2 ± 1.5 Gy and 2.9 ± 1.2 Gy for IMPT_2F and IMPT_3F. The mean dose to the whole heart resulted to 9.9 ± 1.9 Gy for RA_RP compared to 3.7 ± 1.3 Gy or 4.0 ± 1.4 Gy for IMPT_2F or IMPT_3F; the mean dose to the left ventricle resulted to 6.5 ± 1.6 Gy, 1.9 ± 1.5 Gy, 1.9 ± 1.6 Gy respectively. Similar sparing effects were observed for the liver, the kidneys, the stomach, the spleen and the bowels. The EAR per 10,000 patients-years of secondary cancer induction resulted in 19.2 ± 5.7 for RA_RP and 6.1 ± 2.7 for IMPT_2F or 5.7 ± 2.4 for IMPT_3F. The RR for the left ventricle resulted in 1.5 ± 0.1 for RA_RP and 1.1 ± 0.1 for both IMPT sets. For the coronaries, the RR resulted in 1.6 ± 0.4 for RA_RP and 1.2 ± 0.3 for protons. CONCLUSION With regard to cancer of the oesophagogastric junction type I and II, the use of intensity-modulated proton therapy seems to have a clear advantage over VMAT. In particular, the reduction of the heart and abdominal structures dose could result in an optimised side effect profile. Furthermore, reduced risk of secondary neoplasia in the lung can be expected in long-term survivors and would be a great gain for cured patients.

中文翻译：

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局部晚期食管癌新辅助照射中的体积调制弧光治疗与强度调制质子治疗。

背景技术为了研究强度调制质子治疗（IMPT）与体积调制电弧治疗（VMAT）的关系，该技术已通过RapidArc和RapidPlan方法（RA_RP）实现，用于局部晚期食管癌的新辅助放疗。方法回顾性规划20例IMPT（两个字段（IMPT_2F）或三个字段（IMPT_3F））和RA_RP，并根据剂量-体积指标比较结果。确定了肺部继发性癌症诱发的绝对绝对风险（EAR）的估计值。对于心脏结构，估计了冠状动脉疾病（CAD）和慢性心力衰竭（CHF）的相对风险（RR）。结果接近RA_RP和IMPT均允许达到总肿瘤体积（GTV）以及临床和计划目标体积所需的覆盖率，CTV和PTV（对于CTV和GTV，V98％> 98，对于PTV，V95％> 95）。合格指数分别为RA_RP，IMPT_2F和IMPT_3F分别为0.88±0.01、0.89±0.02和0.89±0.02。以相同的顺序，PTV的均匀性指数分别为5.6±0.6％，4.4±0.9％和4.5±0.8％。关于有风险的器官，与RA_RP相比，IMPT计划显示出系统的和统计学上显着的增量保留，特别是对于心脏。RA_RP对合并肺的平均剂量为8.6±2.9 Gy，IMPT_2F和IMPT_3F的平均剂量为3.2±1.5 Gy和2.9±1.2 Gy。RA_RP对整个心脏的平均剂量为9.9±1.9 Gy，而IMPT_2F或IMPT_3F的平均剂量为3.7±1.3 Gy或4.0±1.4 Gy；左心室的平均剂量分别为6.5±1.6 Gy，1.9±1.5 Gy，1.9±1.6 Gy。对于肝，肾，胃，脾和肠观察到类似的节省作用。每10,000患者-年的继发性癌症诱发EAR导致RA_RP的19.2±5.7和IMPT_2F的6.1±2.7或IMPT_3F的5.7±2.4。左心室的RR导致RA_RP为1.5±0.1，两组IMPT均为1.1±0.1。对于冠状动脉，RR导致RA_RP为1.6±0.4，质子为1.2±0.3。结论关于I型和II型食管胃交界处的癌症，使用强度调节质子治疗似乎比VMAT有明显的优势。特别地，减少心脏和腹部结构的剂量可导致最佳的副作用。此外，