Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts.
Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
Int J Radiat Oncol Biol Phys. 2014 Mar 1;88(3):655-63. doi: 10.1016/j.ijrobp.2013.11.239.
The pattern of failure in medulloblastoma patients treated with proton radiation therapy is unknown. For this increasingly used modality, it is important to ensure that outcomes are comparable to those in modern photon series. It has been suggested this pattern may differ from photons because of variations in linear energy transfer (LET) and relative biological effectiveness (RBE). In addition, the use of matching fields for delivery of craniospinal irradiation (CSI) may influence patterns of relapse. Here we report the patterns of failure after the use of protons, compare it to that in the available photon literature, and determine the LET and RBE values in areas of recurrence.
Retrospective review of patients with medulloblastoma treated with proton radiation therapy at Massachusetts General Hospital (MGH) between 2002 and 2011. We documented the locations of first relapse. Discrete failures were contoured on the original planning computed tomography scan. Monte Carlo calculation methods were used to estimate the proton LET distribution. Models were used to estimate RBE values based on the LET distributions.
A total of 109 patients were followed for a median of 38.8 months (range, 1.4-119.2 months). Of the patients, 16 experienced relapse. Relapse involved the supratentorial compartment (n=8), spinal compartment (n=11), and posterior fossa (n=5). Eleven failures were isolated to a single compartment; 6 failures in the spine, 4 failures in the supratentorium, and 1 failure in the posterior fossa. The remaining patients had multiple sites of disease. One isolated spinal failure occurred at the spinal junction of 2 fields. None of the 70 patients treated with an involved-field-only boost failed in the posterior fossa outside of the tumor bed. We found no correlation between Monte Carlo-calculated LET distribution and regions of recurrence.
The most common site of failure in patients treated with protons for medulloblastoma was outside of the posterior fossa. The most common site for isolated local failure was the spine. We recommend consideration of spinal imaging in follow-up and careful attention to dose distribution in the spinal junction regions. Development of techniques that do not require field matching may be of benefit. We did not identify a direct correlation between lower LET values and recurrence in medulloblastoma patients treated with proton therapy. Patterns of failure do not appear to differ from those in patients treated with photon therapy.
接受质子放射治疗的髓母细胞瘤患者的失败模式尚不清楚。对于这种越来越常用的治疗模式，确保其结果与现代光子系列相当非常重要。有人认为，由于线性能量转移 (LET) 和相对生物效应 (RBE) 的差异，这种模式可能与光子不同。此外，使用匹配野来提供颅脊髓照射 (CSI) 可能会影响复发模式。在这里，我们报告了使用质子治疗后失败的模式，将其与现有的光子文献进行了比较，并确定了复发部位的 LET 和 RBE 值。
对 2002 年至 2011 年在马萨诸塞州综合医院 (MGH) 接受质子放射治疗的髓母细胞瘤患者进行回顾性研究。我们记录了首次复发的位置。在原始计划 CT 扫描上勾画离散失败的位置。使用蒙特卡罗计算方法估计质子 LET 分布。根据 LET 分布，使用模型估计 RBE 值。
共有 109 例患者接受了中位随访 38.8 个月（范围，1.4-119.2 个月）。其中 16 例患者复发。复发累及幕上腔（n=8）、脊柱腔（n=11）和后颅窝（n=5）。11 例失败局限于单个部位；6 例在脊柱，4 例在幕上，1 例在后颅窝。其余患者有多个部位的疾病。1 例孤立的脊柱失败发生在 2 个野的脊柱交界处。在仅行累及野加量照射的 70 例患者中，没有 1 例在后颅窝肿瘤床外出现孤立的局部复发。我们发现蒙特卡罗计算的 LET 分布与复发部位之间没有相关性。
接受质子治疗的髓母细胞瘤患者最常见的失败部位是在后颅窝以外。孤立局部失败最常见的部位是脊柱。我们建议在随访中考虑进行脊柱成像，并仔细注意脊柱交界处的剂量分布。开发不需要野匹配的技术可能会有所帮助。我们没有发现接受质子治疗的髓母细胞瘤患者的低 LET 值与复发之间存在直接相关性。失败模式似乎与接受光子治疗的患者没有区别。
