Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
Neurosurgery. 2019 Jun 1;84(6):1242-1250. doi: 10.1093/neuros/nyy176.
The clinical paradigm for spinal tumors with epidural involvement is challenging considering the rigid dose tolerance of the spinal cord. One effective approach involves open surgery for tumor resection, followed by stereotactic body radiotherapy (SBRT). Resection extent is often determined by the neurosurgeon's clinical expertise, without considering optimal subsequent post-operative SBRT treatment.
To quantify the effect of incremental epidural disease resection on tumor coverage for spine SBRT in an effort to working towards integrating radiotherapy planning within the operating room.
Ten patients having undergone spinal separation surgery with postoperative SBRT were retrospectively reviewed. Preoperative magnetic resonance imaging was coregistered to postoperative planning computed tomography to delineate the preoperative epidural disease gross tumor volume (GTV). The GTV was digitally shrunk by a series of fixed amounts away from the cord (up to 6 mm) simulating incremental tumor resection and reflecting an optimal dosimetric endpoint. The dosimetric effect on simulated GTVs was analyzed using metrics such as minimum biologically effective dose (BED) to 95% of the simulated GTV (D95) and compared to the unresected epidural GTV.
Epidural GTV D95 increased at an average rate of 0.88 ± 0.09 Gy10 per mm of resected disease up to the simulated 6 mm limit. Mean BED to D95 was 5.3 Gy10 (31.2%) greater than unresected cases. All metrics showed strong positive correlations with increasing tumor resection margins (R2: 0.989-0.999, P < .01).
Spine separation surgery provides division between the spinal cord and epidural disease, facilitating better disease coverage for subsequent post-operative SBRT. By quantifying the dosimetric advantage prior to surgery on actual clinical cases, targeted surgical planning can be implemented.
考虑到脊髓的刚性剂量耐受，伴有硬膜外受累的脊柱肿瘤的临床范例具有挑战性。一种有效的方法是进行肿瘤切除术的开放性手术，然后进行立体定向体放射治疗（SBRT）。切除范围通常由神经外科医生的临床专业知识决定，而不考虑最佳的术后 SBRT 治疗。
为了量化硬膜外疾病切除对脊柱 SBRT 肿瘤覆盖的影响，努力将放射治疗计划整合到手术室中。
回顾性分析了 10 例接受脊柱分离手术和术后 SBRT 的患者。将术前磁共振成像与术后计划计算机断层扫描进行配准，以描绘术前硬膜外疾病大体肿瘤体积（GTV）。通过一系列固定量的数字缩小 GTV 远离脊髓（最多 6 毫米），模拟递增肿瘤切除术，并反映出最佳的剂量学终点。使用最小生物有效剂量（BED）到模拟 GTV 的 95%（D95）等指标分析模拟 GTV 的剂量学影响，并与未切除的硬膜外 GTV 进行比较。
硬膜外 GTV D95 以平均 0.88 ± 0.09 Gy10/切除疾病的毫米速率增加，直至达到模拟的 6 毫米限制。平均 BED 至 D95 比未切除的病例高 5.3 Gy10（31.2%）。所有指标与肿瘤切除边界的增加呈强烈正相关（R2：0.989-0.999，P<.01）。
脊柱分离手术在脊髓和硬膜外疾病之间提供了分隔，为随后的术后 SBRT 提供了更好的疾病覆盖。通过在实际临床病例上术前量化剂量学优势，可以实施靶向手术计划。
