“That’s Not Achievable”: Evaluation of a Commercial Pre-Plan Feasibility Tool Using TG-218/TG-219 QA Metrics
Abstract
Purpose
To evaluate whether a commercial pre-plan feasibility tool can predict treatment plan achievability and performance against TG-218–recommended measurement-based IMRT QA criteria and TG-219 secondary dose calculation agreement.
Methods
Retrospectively selected clinical IMRT/VMAT plans were evaluated; eight of ten demonstrated either failure to meet TG-218 action limits for measurement-based QA or disagreement exceeding institutional TG-219 tolerances for secondary dose calculation (four measurement-based QA failures, seven secondary check discrepancies). Plans were analyzed using Sun Nuclear Corp. (Melbourne, FL) software, including Pre-Plan Feasibility, DoseCHECK (3D independent dose calculation), and SNC Patient/3DVH (array-based QA/3D dose reconstruction). Feasibility alerts were compared with physician-assigned planning objectives and achieved plan metrics. Target coverage and OAR agreement was evaluated using 3D gamma-based dose comparison and volumetric CTV agreement.
Results
Plans included prostate (n=3), hippocampal avoidance whole brain (HAWB, n=4), and head and neck, anus, and lung (n=1 each). Seven of ten plans were flagged for OAR feasibility concerns related to achieving 100% target coverage at prescription dose. Three plans had planning objectives consistent with feasibility predictions, while four contained dose objectives exceeding feasibility predictions by >50%. Plans with objectives aligned with feasibility predictions met clinical goals without excessive modulation, satisfied TG-218 measurement-based QA action levels (3%/2 mm/global/10% threshold gamma) and demonstrated >90% CTV agreement with TG-219–based secondary dose calculations at 2%/2 mm gamma criteria (all but one). In contrast, all plans with objectives exceeding feasibility predictions either required increased modulation to meet goals (n=2) or failed to meet planning objectives (n=3); all failed at least one TG-218 QA metric.
Conclusion
Pre-plan feasibility predictions correlated with both TG-218 measurement-based QA performance and TG-219 secondary dose calculation agreement. Incorporation of feasibility analysis prior to optimization may reduce unnecessary plan modulation, improve planning efficiency, and decrease late-stage QA-driven plan revisions.