Agenzia Provinciale per la Protonterapia, Trento, Italy.
Radiother Oncol. 2011 Jan;98(1):74-80. doi: 10.1016/j.radonc.2010.10.027. Epub 2010 Dec 20.
To compare helical tomotherapy (HT) and intensity modulated proton therapy (IMPT) on early stage prostate cancer treatments delivered with simultaneous integrated boost (SIB) in moderate hypofractionation.
MATERIAL/METHODS: Eight patients treated with HT were replanned with two-field IMPT (2fIMPT) and five-field IMPT (5fIMPT), using a small pencil beam size (3 mm sigma). The prescribed dose was 74.3 Gy in 28 fractions on PTV1 (prostate) and PTV2 (proximal seminal vesicles), 65.5 Gy on PTV3 (distal seminal vesicles) and on the overlap between rectum and PTVs.
IMPT and HT achieved similar target coverage and dose homogeneity, with 5fIMPT providing the best results. The conformity indexes of IMPT were significantly lower for PTV1+2 and PTV3. Above 65 Gy, HT and IMPT were equivalent in the rectum, while IMPT spared the bladder and the penile bulb from 0 to 70 Gy. From 0 up to 60 Gy, IMPT dosimetric values were (much) lower for all OARs except the femur heads, where HT was better than 2fIMPT in the 25-35 Gy dose range. OARs mean doses were typically reduced by 30-50% by IMPT. NTCPs for the rectum were within 1% between the two techniques, except when the endpoint was stool frequency, where IMPT showed a small (though statistically significant) benefit.
HT and IMPT produce similar dose distributions in the target volume. The current knowledge on dose-effect relations does not allow to quantify the clinical impact of the large sparing of IMPT at medium-to-low doses.
比较螺旋断层放疗（HT）和强度调制质子治疗（IMPT）在中分割同步推量（SIB）治疗早期前列腺癌中的应用。
材料/方法：对 8 例接受 HT 治疗的患者进行了两野 IMPT（2fIMPT）和五野 IMPT（5fIMPT）的再计划，采用小铅笔束大小（3mm sigma）。PTV1（前列腺）和 PTV2（近端精囊）的处方剂量为 74.3Gy/28 次，PTV3（远端精囊）和直肠与 PTV 重叠部位的处方剂量为 65.5Gy。
IMPT 和 HT 实现了相似的靶区覆盖和剂量均匀性，5fIMPT 提供了最佳结果。PTV1+2 和 PTV3 的适形指数 IMPT 显著降低。在直肠中，HT 和 IMPT 在 65Gy 以上时等效，而 IMPT 使膀胱和阴茎球免于 0 至 70Gy 的照射。在 0 至 60Gy 范围内，除股骨头部外，IMPT 的所有 OARs 的剂量学值都（明显）低于 HT，在 25-35Gy 剂量范围内，HT 优于 2fIMPT。OARs 平均剂量通常通过 IMPT 降低 30-50%。两种技术的直肠 NTCP 差异在 1%以内，除了终点为粪便频率时，IMPT 显示出较小（尽管具有统计学意义）的优势。
HT 和 IMPT 在靶区产生相似的剂量分布。目前关于剂量-效应关系的知识还无法量化 IMPT 在中低剂量下大量保护的临床影响。
