Revisiting Treatment of Spine Metastases In the Era of Acuros
Abstract
Purpose
To determine whether clinical quality metrics and treatment goals previously believed to be achieved using the AAA algorithm remain valid when recalculated with Acuros (AXB) in postoperative spine metastasis treatment using 3D conformal radiotherapy (3DCRT). Dose calculation algorithm choice may significantly impact perceived treatment quality, particularly in heterogeneous postoperative cases with implanted spinal hardware. In these scenarios, dose perturbations can be substantial, necessitating detailed evaluation of target coverage, dose to OARs, and overall treatment goals.
Methods
In this retrospective study, clinical plans (n = 41) originally calculated using AAA were recalculated with AXB with identical field arrangements and monitor units. The cohort included postoperative (n=20) cases across cervical to lumbar spine, treated with 3DCRT. Non-operative cases (n=21) were included for comparison. Dosimetric endpoints included PTV V95%, cord V105%, and target heterogeneity index.
Results
Largest dosimetric differences were observed in postoperative 3DCRT plans. Notable differences were seen in non-operative cases. In postoperative 3DCRT, key findings included increased cold spots, reduced target coverage, higher cord dose, and greater heterogeneity when recalculated with AXB: V95% decreased from 98% ± 2% (AAA) to 93% ± 7% (AXB), cord V105% increased from 24% ± 22% to 32% ± 29%, and HI increased from 27% to 48%. In non-op cases results were: V95% decreased from 99% ± 3% (AAA) to 93% ± 12% (AXB), cord V105% decreased from 23% ± 33% to 21% ± 32%, and HI increased from 21% to 25%.
Conclusion
Our results demonstrate that reliance on AAA – especially for postoperative 3DCRT – can mask clinically meaningful underdosing and heterogeneity that are only exposed by Acuros. These findings reinforce that algorithm choice fundamentally alters clinically perceived plan quality and should be considered an essential treatment defining decision making tool to accurately interpret target coverage, tumor control, and neurological risk in spine radiotherapy.