The advantage of 3D conformal treatment of lumbar spine metastases in comparison to traditional PA or AP-PA techniques: restoring an intermediate niche of therapeutic sophistication

BACKGROUND To evaluate the effect of the 3D radiation field design on normal tissues compared with commonly used appositional fields in patients with lumbar spine metastases. METHODS AND MATERIALS Ten comparative treatment plans for radiation of lumbar spine metastases were compared for posterior and anterior- posterior fields with 3D plans. RESULTS The PTV coverage in all comparative plans was similar. V 15 of the bowel in 3D, AP-PA and PA plans was 6.7 Gy (SD 6.47), 39.8 Gy (SD 11.4) and 37.3 Gy (SD15.7), respectively (p < 0.0001). The mean dose to both kidneys was 9.6 Gy (SD 4.8), 4.1 Gy (SD 3.9) and 4.6 Gy (SD 4.4) for appropriate plans (p = 0.002). Maximal dose to the spinal cord was 30.6 Gy (SD 2.1), 33.1 Gy (SD 9.8) and 37.7 Gy (SD 2) for 3D, AP-PA and PA plans. CONCLUSION 3D conformal treatment planning of lumbar vertebral metastases was significantly better in term of bowel and spinal cord exposure compared to AP-PA and PA techniques. The exposure of the kidneys in 3D plans, while greater than in the comparative plans, did not violate accepted dose-volume thresholds.