A comparison of sensitivity and specificity of dosimetry audits for intensity modulated radiation therapy used internationally for clinical trial credentialing.

Abstract

Assess consistency of end-to-end dosimetry audits used by six Global Quality Assurance of Radiation Therapy Clinical Trials Harmonization Group (GHG) member organizations to harmonise audits and reduce audit overlap in multinational trials while maintaining quality. Prior work developed and validated 16 head and neck reference plans, based on established international dosimetry audits for intensity modulated radiotherapy treatments. Realistic modifications, developed from reported variations in clinical practice, were introduced into nine copies of each plan, generating 144 modified plans. These plans were grouped as acceptable (should pass) and unacceptable (should fail) using plan assessment metrics and action limits on CTV_mean, CTV_D95, and OAR_D0.03cc. In the current work, each GHG audit system measured the error-free reference plans on its own phantom using its standard workflow. The measured error-free plans were then compared to the dose calculations of the modified plans. Outcomes were expressed as pass/fail, which were then compared to the "should pass/should fail" benchmark to determine the sensitivity and specificity of each system. An optimal action limit was determined for each audit system to achieve a common sensitivity across all audit systems. All audit systems reliably identified failing plans (sensitivity 0.92-1.0; specificity 0.40-0.91) with 5% ΔCTV_mean assessment action thresholds. Adjusting the action limit revealed that each audit system was tuned to detect different error thresholds (3.3% - 5.7%). Changing audit system action limits specificity, while preserving system sensitivity. The comparably high sensitivity across all audit systems could allow harmonising of dosimetry audits for clinical trials on an international scale based on sensitivity alone. Future work harmonising specificity would help streamline credentialing for international clinical trials.