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Abstract：
Background and purpose: Proton therapy has been shown to provide dosimetric benefits in comparison with IMRT when treating prostate cancer with whole pelvis radiation; however, the optimal proton beam arrangement has yet to be established. The aim of this study was to evaluate three different intensity-modulated proton therapy (IMPT) beam arrangements when treating the prostate bed and pelvis in the postoperative setting. Materials and Methods: Twenty-three post-prostatectomy patients were planned using three different beam arrangements: two-field (IMPT2B) (opposed laterals), three-field (IMPT3B) (opposed laterals inferiorly matched to a posterior-anterior beam superiorly), and four-field (IMPT4B) (opposed laterals inferiorly matched to two posterior oblique beams superiorly) arrangements. The prescription was 50 Gy radiobiological equivalent (GyE) to the pelvis and 70 GyE to the prostate bed. Comparisons were made using paired two-sided Wilcoxon signed-rank tests. Results: CTV coverages were met for all IMPT plans, with 99% of CTVs receiving ≥ 100% of prescription doses. All organ at risk (OAR) objectives were met with IMPT3B and IMPT4B plans, while several rectum objectives were exceeded by IMPT2B plans. IMPT4B provided the lowest doses to OARs for the majority of analyzed outcomes, with significantly lower doses than IMPT2B +/- IMPT3B for bladder V30-V50 and mean dose; bowel V15-V45 and mean dose; sigmoid maximum dose; rectum V40-V72.1, maximum dose, and mean dose; femoral head V37-40 and maximum dose; bone V40 and mean dose; penile bulb mean dose; and skin maximum dose. Conclusion: This study is the first to compare proton beam arrangements when treating the prostate bed and pelvis. four-field plans provided better sparing of the bladder, bowel, and rectum than 2- and three-field plans. The data presented herein may help inform the future delivery of whole pelvis IMPT for prostate cancer.
摘要：
背景和目的：与IMRT相比，质子疗法已被证明在使用全骨盆放射治疗前列腺癌时具有剂量学益处；然而，最佳质子束排列尚未建立。这项研究的目的是在术后治疗前列腺床和骨盆时评估三种不同的强度调节质子治疗（IMT）束布置。材料和方法：23名前列腺切除术后患者计划使用三种不同的束布置：两野（IMPT2B）（相对侧），三视野（IMPT3B）（相对侧翼与后前束上方匹配），和四场（IMPT4B）（相对的侧面向下匹配两个后斜梁）布置。处方为骨盆50Gy放射生物学当量（GyE），前列腺床70GyE。使用配对的双侧Wilcoxon符号秩检验进行比较。结果：所有IMPT计划均符合CTV覆盖范围，99%的CTV接受≥100%的处方剂量。IMPT3B和IMPT4B计划符合所有器官风险（OAR）目标，而IMPT2B计划超过了几个直肠目标。IMPT4B为大多数分析结果提供了OAR的最低剂量，膀胱V30-V50和平均剂量明显低于IMPT2B+/-IMPT3B；肠V15-V45和平均剂量；乙状结肠最大剂量；直肠V40-V72.1，最大剂量，和平均剂量；股骨头V37-40和最大剂量；骨V40和平均剂量；阴茎球平均剂量；和皮肤最大剂量。结论：这项研究首次比较了治疗前列腺床和骨盆时的质子束排列。四野计划提供了更好的膀胱保留，肠,和直肠比2和3场计划。本文呈现的数据可以帮助告知用于前列腺癌的整个骨盆IMPT的未来递送。
