Novel Brachytherapy Device for Dural Irradiation

描述(申请人提供)：胸椎和腰椎肿瘤通常延伸到椎管内并侵袭硬脑膜，通常渗透到椎管的表层。这种肉瘤细胞向硬脑膜表面的渗透是这些患者无法接受侵袭性手术治愈的主要原因。使用外束放射治疗，大多数肿瘤床可以被治疗到有效剂量水平。然而，由于脐带非常接近，硬脑膜的剂量必须被限制在远低于所需的治疗范围。因此，为了在不过度照射脊髓的情况下增加硬脑膜表面的剂量，建议在术中使用专门制造的贝塔辐射装置补充剂量。额外提供的剂量将以非常小的风险和对患者潜在的巨大好处显著增加肿瘤控制的可能性。 在该计划的第一阶段，开发了一种“原则证明”装置。在第一阶段计划成功结果的基础上，马萨诸塞州总医院的医生在临床上使用了“原则证明”装置，成功地治疗了7名患有脊椎或椎旁肿瘤的适当患者，并根据IRB批准的方案评估了患者的耐受性和结果。采用现有斑块设计的放射肿瘤学家已经确定了一些特征，这些特征将导致剂量传递的改善。该计划的具体目标是在第一阶段计划期间开发的“原则证明”之外，进一步开发这种近距离放射治疗设备。将开发一种可定制的几何斑块，以提高剂量分布与治疗目标的一致性。这将包括改善剂量下降的不同负荷、将解剖特征纳入斑块配置的改进方法，以及在激活之前制造完整斑块的方法，以促进实现更复杂的几何形状和减少辐射危险。由此产生的斑块及其剂量学将通过人体试验评估其临床用途。这项评估的结果将导致该设备的最佳设计，为临床使用做准备。

DESCRIPTION (provided by applicant): Tumors of the thoracic and lumbar spine commonly extend into the vertebral canal and impinge on the dura, often infiltrating its superficial layers. This infiltration of sarcoma cells into the dura surface is a major cause of failure of aggressive surgery to obtain cure of these patients. With external beam radiation therapy, the majority of the tumor bed can be treated to effective dose levels. However, because of the close proximity of the cord, the dose to the dura must be limited to well below the desired treatment range. Therefore, to increase the dose to the dural surface without over-irradiating the cord, it is proposed to intraoperatively deliver a supplemental dose using a specially made beta-emitting radioactive device. The additional dose delivered will, at very small risk and potentially great advantage to the patient, markedly increase the probability of tumor control. During Phase I of this program, a "proof of principle" device was developed. On the basis of the successful results of the Phase I program, physicians at the Massachusetts General Hospital have clinically employed the "proof of principle" device to successfully treat seven appropriate patients with vertebral or paravertebral tumors, and assess patient tolerance and outcome under an IRB approved protocol. Radiation oncologists who have employed the existing plaque design have identified a number of features that would result in improved dose delivery. The specific aim of this program is to further develop this brachytherapy device beyond the "proof of principle" developed during the Phase I program. A customizable geometry plaque will be developed to improve the conformity of the dose distribution to the treatment target. This will include differential loading to improve dose drop-off, an improved method of incorporating anatomical features into the plaque configuration, and methods for manufacturing completed plaques before activation to facilitate achieving more complex geometries and reducing the radiation hazard. The resultant plaque and its dosimetry will be evaluated for clinical utility through a human trial. The results of this evaluation will lead to an optimum design of this device, in preparation for clinical use.