Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Division of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Int J Radiat Oncol Biol Phys. 2021 Mar 1;109(3):718-725. doi: 10.1016/j.ijrobp.2020.09.050.
Pediatric patients with rhabdomyosarcoma (RMS) are treated with multimodal therapy, often with radiation therapy (RT) as part of local therapy. We report on the efficacy and patterns of failure after proton beam therapy (PBT) for RMS.
Between January 2006 and February 2017, patients with RMS were enrolled in a prospective institutional review board-approved registry protocol for pediatric patients undergoing PBT. Demographics, clinical characteristics, and treatment related outcomes were reviewed.
Ninety-four RMS patients were treated with a combination of chemotherapy (CT) and PBT. The majority of patients had head and neck (49%) and genitourinary (30%) primaries. Median tumor size was 4.1 cm (range, 1.0-16.5 cm); 33 patients (35%) had primary tumors >5 cm. Median cyclophosphamide equivalent dose was 14.4 g/m (range, 0-30.8 g/m). Median time from CT initiation to RT initiation was 13 weeks (range, 1-58 weeks). With median follow-up of 4 years, 4-year overall survival (OS) was 71%, and 4-year progression-free survival (PFS) was 63%. Thirty patients (32%) experienced relapse (13% with local failure [LF]). Four-year local control (LC) was 85% overall; 4-year LC rates were 100% for low-risk, 85% for intermediate-risk, and 55% for high-risk patients (P = .02). Tumor size predicted LC (P = .007), with 7% versus 33% LF rate by tumor size (≤5 cm vs >5 cm). Delayed RT delivery (≥13 weeks from initiation of CT) predicted worse LC (P = .01). Increased tumor size predicted both inferior PFS (P = .02) and OS (P = .01). Delayed RT delivery predicted both inferior PFS (P = .04) and OS (P = .03).
PBT provides LC comparable to prior studies using photon RT. Inferior LC, PFS, and OS rates were observed for patients with larger tumors and those treated with delayed RT. This finding supports ongoing prospective efforts to dose-escalate treatment of tumors >5 cm; however, these data call into question the optimal timing of local therapy, particularly for patients treated with reduced-dose cyclophosphamide.
横纹肌肉瘤（RMS）患儿采用多模式治疗，常采用放射治疗（RT）作为局部治疗的一部分。我们报告质子束治疗（PBT）治疗 RMS 的疗效和失败模式。
2006 年 1 月至 2017 年 2 月期间，患有 RMS 的患者参加了一项前瞻性机构审查委员会批准的登记研究，该研究用于接受 PBT 的儿科患者。回顾了人口统计学、临床特征和治疗相关结局。
94 例 RMS 患者接受了化疗（CT）和 PBT 的联合治疗。大多数患者有头颈部（49%）和泌尿生殖系统（30%）原发性肿瘤。肿瘤大小中位数为 4.1cm（范围 1.0-16.5cm）；33 例（35%）患者的原发性肿瘤>5cm。环磷酰胺等效剂量中位数为 14.4g/m（范围 0-30.8g/m）。从 CT 开始到 RT 开始的中位时间为 13 周（范围 1-58 周）。中位随访 4 年后，4 年总生存率（OS）为 71%，4 年无进展生存率（PFS）为 63%。30 例（32%）患者出现复发（13%为局部失败[LF]）。整体 4 年局部控制（LC）率为 85%；低危患者 4 年 LC 率为 100%，中危患者为 85%，高危患者为 55%（P=0.02）。肿瘤大小预测 LC（P=0.007），肿瘤大小（≤5cm 与>5cm）的 LF 率分别为 7%和 33%。延迟 RT （CT 起始后≥13 周）可预测 LC 不良（P=0.01）。肿瘤增大预测 PFS（P=0.02）和 OS（P=0.01）均降低。延迟 RT 预测 PFS（P=0.04）和 OS（P=0.03）均降低。
PBT 提供的 LC 与使用光子 RT 的先前研究相当。肿瘤较大和接受延迟 RT 的患者的 LC、PFS 和 OS 率较低。这一发现支持正在进行的针对>5cm 肿瘤进行剂量递增治疗的前瞻性努力；然而，这些数据对局部治疗的最佳时机提出了质疑，特别是对于接受低剂量环磷酰胺治疗的患者。
