Purpose: Given that the current standard of proton therapy (PT) for prostate cancer is through bilateral beams, this modality is typically avoided when it comes to treatment of patients with hip prosthesis. The purpose of this study was to evaluate whether novel PT methods, i.e., anterior proton beams and proton arc therapy (PArc), could be feasible options to treat this patient subpopulation. We evaluate PT methods in the context of dosimetry and robustness and compare with standard of practice volumetric modulated arc therapy (VMAT) to explore any potential benefits. Methods: Two PT and one VMAT treatment plans were retrospectively created for 10 patients who participated in a clinical trial with a weekly repeat CT (rCT) imaging component. All plans were robustly optimized and featured: (1) combination anterior oblique and lateral proton beams (AoL), (2) PArc, and (3) VMAT. All patients had hydrogel spacers in place, which enabled safe application of anterior proton beams. The planned dose was 70 Gy (RBE) to the entire prostate gland and 50 Gy (RBE) to the proximal seminal vesicles in 28 fractions. Along with plan dose–volume metrics, robustness to setup and interfractional variations were evaluated using the weekly rCT images. The linear energy transfer (LET)-weighted dose was evaluated for PArc plans to ensure urethra sparing given the typical high-LET region at the end of range. Results: Both PT methods were dosimetrically feasible and provided reduction of some key OAR metrics compared to VMAT except for penile bulb, while providing equally good target coverage. Significant differences in median rectum V35 (22–25%), penile bulb Dmean (5 Gy), rectum V61 (2%), right femoral head Dmean (5 Gy), and bladder V39 (4%) were found between PT and VMAT. All plans were equally robust to variations. LET-weighted dose in urethra was equivalent to the physical dose for PArc plans and hence no added urethral toxicity was expected. Conclusions: PT for treatment of prostate cancer patients with hip prosthesis is feasible and equivalent or potentially superior to VMAT in quality in some cases. The choice of radiotherapy regimen can be personalized based on patient characteristics to achieve the best treatment outcome.
目的：鉴于当前前列腺癌质子治疗（PT）的标准方案采用双侧束流，对于髋关节假体患者，通常避免采用此疗法。本研究旨在评估新型质子治疗方法，即前向质子束流和质子弧治疗（PArc），是否可作为治疗此类患者亚群的可行选择。我们从剂量学和鲁棒性角度评估质子治疗方法，并与现行标准的容积旋转调强放疗（VMAT）进行比较，以探索其潜在优势。 方法：针对10名参与每周重复CT（rCT）影像临床试验的患者，回顾性制定了两种质子治疗计划和一种VMAT计划。所有计划均经过鲁棒性优化，包括：（1）前斜向与侧向质子束流组合（AoL），（2）PArc，以及（3）VMAT。所有患者均植入水凝胶间隔物，以确保前向质子束流的安全应用。计划剂量为全前列腺70 Gy（RBE）和近端精囊50 Gy（RBE），分28次完成。除计划剂量-体积指标外，还利用每周rCT图像评估了计划对摆位误差和分次间变动的鲁棒性。针对PArc计划评估了线性能量转移（LET）加权剂量，以确保在射程末端典型高LET区域对尿道的保护。 结果：两种质子治疗方法在剂量学上均可行，与VMAT相比，除阴茎球部外，其他关键危及器官指标均有所降低，同时靶区覆盖效果相当。质子治疗与VMAT在直肠V35中位值（22–25%）、阴茎球部平均剂量（5 Gy）、直肠V61（2%）、右侧股骨头平均剂量（5 Gy）和膀胱V39（4%）方面存在显著差异。所有计划对变动的鲁棒性相当。PArc计划的尿道LET加权剂量与物理剂量等效，因此预计不会增加尿道毒性。 结论：对于髋关节假体前列腺癌患者，质子治疗是可行的，在某些情况下其治疗质量与VMAT相当或可能更优。可根据患者个体特征个性化选择放疗方案，以实现最佳治疗效果。
The Role of Proton Therapy for Prostate Cancer in the Setting of Hip Prosthesis
肿瘤(癌症)患者之家