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.
背景与目的：在全盆腔放射治疗前列腺癌时，质子治疗相比调强放射治疗（IMRT）已显示出剂量学优势，但最佳质子束流排布方案尚未确立。本研究旨在评估术后前列腺床及盆腔治疗中三种不同调强质子治疗（IMPT）束流排布方案的优劣。 材料与方法：对23例前列腺切除术后患者设计三种束流排布方案：双野（IMPT2B）（对穿侧野）、三野（IMPT3B）（下方对穿侧野与上方前后野匹配）及四野（IMPT4B）（下方对穿侧野与上方两个后斜野匹配）。处方剂量为盆腔50 Gy放射生物学等效剂量（GyE），前列腺床70 GyE。采用配对双侧Wilcoxon符号秩检验进行比较分析。 结果：所有IMPT计划均满足临床靶区（CTV）覆盖要求，99%的CTV接受≥100%处方剂量。IMPT3B和IMPT4B计划均满足所有危及器官（OAR）剂量约束，而IMPT2B计划部分直肠剂量约束超标。在多数分析指标中，IMPT4B对OAR的照射剂量最低，相较于IMPT2B及IMPT3B，其在膀胱V30–V50及平均剂量；肠道V15–V45及平均剂量；乙状结肠最大剂量；直肠V40–V72.1、最大剂量及平均剂量；股骨头V37–40及最大剂量；骨骼V40及平均剂量；阴茎球部平均剂量；皮肤最大剂量等参数上均显著降低。 结论：本研究首次比较了前列腺床及盆腔质子治疗的束流排布方案。四野计划在保护膀胱、肠道和直肠方面优于双野及三野计划。本研究数据可为未来前列腺癌全盆腔IMPT治疗提供重要参考。
肿瘤(癌症)患者之家