Transitioning from conventional photon therapy to proton therapy for primary brain tumors

Proton radiation therapy (PT) has become a treatment option alongside photon therapy (XRT) for lower-grade gliomas (LGG). In this single-institution retrospective study, we investigate the patient characteristics and treatment outcomes, including pseudo-progression (PsP), for LGG patients selected for PT. Adult patients with grade 2–3 glioma consecutively treated with radiotherapy (RT) from May 2012 to December 2019 were retrospectively included in this cohort study. Tumor characteristics and treatment data were collected. The groups treated with PT and XRT were compared regarding treatment characteristics, side effects, occurrence of PsP, and survival outcomes. PsP was defined as new or growing lesions followed by either decrease or stabilization during a 12 month-period with no treatment. Out of 143 patients meeting the inclusion criteria, 44 were treated with PT, 98 with XRT and one with mixed PT + XRT. The patients receiving PT were younger, had a lower tumor grade, more oligodendrogliomas and received a lower mean brain and brainstem dose. PsP was observed in 21 out of 126 patients, with no difference between XRT and PT (<i>p</i> = .38). The rate of fatigue in immediate connection to RT (zero to three months after) was higher for XRT than for PT (<i>p</i> = .016). The PT patients had a significantly better PFS and OS than the XRT patients (<i>p</i> = .025 and .035), but in multivariate analysis radiation modality was non-significant. Higher average dose to both brain and brainstem was associated with inferior PFS and OS (<i>p</i> &lt; .001). Median follow-up time were 69 months and 26 months for XRT and PT patients, respectively. Contrary to previous studies, there was no difference in risk of PsP for XRT and PT. PT was associated with lower rates of fatigue &lt;3 months after RT. The superior survival outcomes for PT indicates that the patients with the best prognosis were referred to PT.

质子放射治疗（Proton radiation therapy, PT）现已成为与光子放射治疗（Photon therapy, XRT）并列的低级别胶质瘤（lower-grade gliomas, LGG）治疗选择。本项单中心回顾性研究针对纳入质子治疗的低级别胶质瘤患者，探讨其患者特征与治疗结局，包括假性进展（pseudo-progression, PsP）发生情况。本队列研究回顾性纳入2012年5月至2019年12月期间连续接受放射治疗（radiotherapy, RT）的2~3级胶质瘤成年患者，收集了患者的肿瘤特征与治疗相关数据，并对比接受PT与XRT治疗的两组患者在治疗特征、不良反应、假性进展发生率及生存结局方面的差异。假性进展被定义为出现新发或进展性病灶后，在未采取额外治疗的12个月随访周期内，病灶出现缩小或趋于稳定。最终共有143例符合纳入标准的患者入组，其中44例接受PT治疗，98例接受XRT治疗，1例接受PT与XRT联合治疗。相较于XRT组，PT组患者年龄更轻、肿瘤分级更低、少突胶质细胞瘤占比更高，且接受的全脑与脑干平均辐射剂量更低。126例患者中共有21例出现假性进展，XRT组与PT组的假性进展发生率无显著统计学差异（p = 0.38）。放疗后即刻（0~3个月内）的疲劳发生率，XRT组显著高于PT组（p = 0.016）。PT组患者的无进展生存期（progression-free survival, PFS）与总生存期（overall survival, OS）均显著优于XRT组（p = 0.025与0.035），但在多因素分析中，放射治疗方式并非独立影响因素。全脑与脑干的平均辐射剂量升高与更差的无进展生存期和总生存期显著相关（p < 0.001）。XRT组与PT组患者的中位随访时间分别为69个月与26个月。与既往研究结论相悖，本研究未发现XRT与PT在假性进展风险上存在显著差异。PT治疗与放疗后3个月内更低的疲劳发生率相关。PT组更优的生存结局提示，预后更佳的患者被转诊接受了质子放射治疗。