一种治疗转移性癌症患者的质子-光子联合治疗新方法。

A new approach to combined proton-photon therapy for metastatic cancer patients.

机构信息

Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.

出版信息

Phys Med Biol. 2024 Jul 9;69(14). doi: 10.1088/1361-6560/ad5d48.

PMID:38942008

Abstract

Proton therapy is a limited resource and is typically not available to metastatic cancer patients. Combined proton-photon therapy (CPPT), where most fractions are delivered with photons and only few with protons, represents an approach to distribute proton resources over a larger patient population. In this study, we consider stereotactic radiotherapy of multiple brain or liver metastases, and develop an approach to optimally take advantage of a single proton fraction by optimizing the proton and photon dose contributions to each individual metastasis.CPPT treatments must balance two competing goals: (1) deliver a larger dose in the proton fractions to reduce integral dose, and (2) fractionate the dose in the normal tissue between metastases, which requires using the photon fractions. Such CPPT treatments are generated by simultaneously optimizing intensity modulated proton therapy (IMPT) and intensity modulated radiotherapy (IMRT) plans based on their cumulative biologically effective dose (BED). The dose contributions of the proton and photon fractions to each individual metastasis are handled as additional optimization variables in the optimization problem. The method is demonstrated for two patients with 29 and 30 brain metastases, and two patients with 4 and 3 liver metastases.Optimized CPPT plans increase the proton dose contribution to most of the metastases, while using photons to fractionate the dose around metastases which are large or located close to critical structures. On average, the optimized CPPT plans reduce the mean brain BEDby 29% and the mean liver BEDby 42% compared to IMRT-only plans. Thereby, the CPPT plans approach the dosimetric quality of IMPT-only plans, for which the mean brain BEDand mean liver BEDare reduced by 28% and 58%, respectively, compared to IMRT-only plans.CPPT with optimized proton and photon dose contributions to individual metastases may benefit selected metastatic cancer patients without tying up major proton resources.

摘要

质子治疗是一种有限的资源，通常无法用于转移性癌症患者。质子-光子联合治疗（CPPT），其中大多数分次采用光子治疗，只有少数分次采用质子治疗，代表了一种在更大的患者群体中分配质子资源的方法。在这项研究中，我们考虑了多个脑或肝转移的立体定向放射治疗，并开发了一种方法，通过优化每个转移灶的质子和光子剂量贡献，来最优地利用单次质子分次。CPPT 治疗必须平衡两个相互竞争的目标：（1）在质子分次中给予更大剂量，以降低积分剂量，（2）在转移灶之间的正常组织中进行分次，这需要使用光子分次。这种 CPPT 治疗是通过同时优化强度调制质子治疗（IMPT）和强度调制放射治疗（IMRT）计划，并基于它们的累积生物有效剂量（BED）来生成的。质子和光子分次对每个转移灶的剂量贡献被视为优化问题中的附加优化变量。该方法在两名有 29 个和 30 个脑转移灶的患者以及两名有 4 个和 3 个肝转移灶的患者中得到了验证。优化后的 CPPT 计划增加了大多数转移灶的质子剂量贡献，同时使用光子在大或靠近关键结构的转移灶周围进行剂量分次。平均而言，与仅接受 IMRT 治疗的计划相比，优化后的 CPPT 计划可降低脑 BED 的平均值 29%，降低肝 BED 的平均值 42%。因此，CPPT 计划接近仅接受 IMPT 治疗的计划的剂量学质量，与仅接受 IMRT 治疗的计划相比，脑 BED 的平均值降低 28%，肝 BED 的平均值降低 58%。对于选定的转移性癌症患者，优化后的 CPPT 计划可能会受益于针对个体转移灶的质子和光子剂量贡献，而不会占用主要的质子资源。