Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Department of Oncology, Xiangya Hospital of Central South University, Changsha, People's Republic of China.
Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Int J Radiat Oncol Biol Phys. 2021 Jul 15;110(4):984-992. doi: 10.1016/j.ijrobp.2021.02.018. Epub 2021 Feb 16.
Uncertainties in relative biological effectiveness (RBE) constitute a major pitfall of the use of protons in clinics. An RBE value of 1.1, which is based on cell culture and animal models, is currently used in clinical proton planning. The purpose of this study was to determine RBE for temporal lobe radiographic changes using long-term follow-up data from patients with nasopharyngeal carcinoma.
Five hundred sixty-six patients with newly diagnosed nasopharyngeal carcinoma received double-scattering proton therapy or intensity modulated radiation therapy at our institutions. The 2 treatment cohorts were well matched. Proton dose distributions were simulated using Monte Carlo and compared with those obtained from the proton clinical treatment planning system. Late treatment effect was defined as development of enhancement of temporal lobe on T1-weighted magnetic resonance imaging, with or without accompanying clinical symptoms. The tolerance dose was calculated with receiving operator characteristic analysis and the Youden index. Tolerance curves, expressed as a cumulative dose-volume histogram, were generated using the cutoff points.
With a median follow-up period >5 years for both cohorts, 10% of proton patients and 4% of patients undergoing intensity modulated radiation therapy developed temporal lobe enhancement in unilateral temporal lobe. There was no significant difference in dose distributions between the Monte Carlo method and treatment planning system. The tolerance dose-volume levels were V10 (26.1%), V20 (21.9%), V30 (14.0%), V40 (7.7%), V50 (4.8%), and V60 (3.3%) for proton therapy (P < .03). Comparison of the two tolerance curves revealed that tolerance doses of proton treatments were lower than that of photon treatments at all dose levels. The dose tolerance at D1% was 58.56 Gy for protons and 69.07 Gy for photons. The RBE for temporal lobe enhancement from proton treatments were calculated to be 1.18.
Using long-term clinical outcome of patients with nasopharyngeal carcinoma, our data suggest that the RBE for temporal lobe enhancement is 1.18 at D1%. A prospective study in a large cohort would be necessary to confirm these findings.
相对生物学效应（RBE）的不确定性是质子在临床应用中的主要陷阱。目前，临床质子计划中使用的 RBE 值为 1.1，该值基于细胞培养和动物模型得出。本研究旨在使用鼻咽癌患者的长期随访数据来确定颞叶放射性变化的 RBE。
566 例初诊鼻咽癌患者在我们的机构接受双散射质子治疗或强度调制放射治疗。这 2 个治疗组匹配良好。使用蒙特卡罗方法模拟质子剂量分布，并与质子临床治疗计划系统获得的剂量分布进行比较。晚期治疗效果定义为 T1 加权磁共振成像上颞叶增强，伴有或不伴有伴随临床症状。使用接收者操作特征分析和 Youden 指数计算耐受剂量。使用截断点生成表示累积剂量-体积直方图的耐受曲线。
对于两个队列，中位随访时间均超过 5 年，10%的质子患者和 4%的调强放疗患者单侧颞叶出现颞叶增强。蒙特卡罗方法与治疗计划系统之间的剂量分布无显著差异。质子治疗的耐受剂量-体积水平分别为 V10（26.1%）、V20（21.9%）、V30（14.0%）、V40（7.7%）、V50（4.8%）和 V60（3.3%）（P<0.03）。比较两条耐受曲线发现，在所有剂量水平下，质子治疗的耐受剂量均低于光子治疗。质子治疗的 D1%剂量耐受为 58.56 Gy，光子治疗的 D1%剂量耐受为 69.07 Gy。质子治疗颞叶增强的 RBE 计算为 1.18。
使用鼻咽癌患者的长期临床结果，我们的数据表明，D1%时颞叶增强的 RBE 为 1.18。需要在大队列中进行前瞻性研究来证实这些发现。
