Automated contouring and radiotherapy treatment planning of spine metastases using atlas-based auto-segmentation and knowledge-based planning approaches.

Abstract

Objectives: Uncomplicated spine metastases are routinely treated with conventional external beam radiotherapy (cEBRT). In cEBRT, there is no delineation of target volumes or organs at risk (OAR), or attempt to optimise dose distribution to deliver conformal, homogeneous dose distributions with sparing of OAR. Atlas-based auto-segmentation (ABAS) for target volume and OAR delineation, followed by knowledge-based planning (KBP) could facilitate conformal planning of spine metastases.

Methods: ABAS using SmartSegmentation for delineation of thoracic and lumbar vertebrae, and OAR in their vicinity, provided target volumes and OAR for conformal treatment planning. 30 volumetric-modulated arc therapy (VMAT) treatment plans were produced using RapidPlan KBP. Plans produced using this automated approach were compared to the equivalent cEBRT treatment plans.

Results: Target volume coverage for RapidPlan VMAT generated plans was superior to cEBRT. PTV Dmean = 7.86 ± 0.16 Gy, Dmin = 3.46 ± 1.79 Gy, Dmax = 8.56 ± 0.05 Gy for RapidPlan VMAT compared to Dmean = 7.78 ± 0.24 Gy, Dmin = 1.83 ± 1.08 Gy, Dmax = 10.46 ± 0.41 Gy for cEBRT. With homogeneity index and conformity index 0.236 ± 0.215 and 1.201 ± 0.121 respectively for RapidPlan VMAT compared to 0.508 ± 0.137 and 1.789 ± 0.437 for cEBRT. Dose to dose-limiting OAR spinal cord and cauda equina was reduced for RapidPlan VMAT, with Dmax of 7.91 ± 0.16 Gy and 7.94 ± 0.13 Gy respectively compared to 8.67 ± 0.13 Gy and 8.90 ± 0.16 Gy for cEBRT. KBP was superior to cEBRT in terms of target coverage, homogeneity and conformity and was achievable in a clinically acceptable time, with improved sparing of the spinal cord and cauda equina.

Conclusions: Implementation of automated treatment planning for uncomplicated spine metastases is feasible in the clinical environment with superior plan quality compared to cEBRT.

Advances in knowledge: Automated contouring and treatment planning are feasible in the clinical environment using this approach and would allow patients conformal as opposed to conventional external beam radiotherapy for treatment of spine metastases.