Improving Quality and Consistency in Clinical Trials via Knowledge-Based Planning, NRG Oncology RTOG 0631

Abstract

Consistency and standardization of radiotherapy planning quality for conducting a multi-institutional clinical trial are always challenging, and non-protocol compliant radiotherapy plans have been shown to impact patient outcomes. This study was aimed to utilize knowledge-based planning (KBP) as a method of producing high quality, consistent, protocol compliant treatment plans, in a complex setting of spine SBRT on RTOG 0631. An internally developed KBP model was applied to an external validation cohort of 22 anonymized cases submitted to NRG for RTOG 0631. The original and KBP plans were compared via their protocol scores, target conformity and gradient index, dose to critical structures, and dose to surrounding normal tissues. The KBP model generated plans meeting all protocol objectives in a single optimization when tested on both internal and external RTOG 0631 cases. Two external plans that were considered to have a protocol-unacceptable deviation were made protocol compliant through the use of the model. There were no statistically significant differences in conformity or gradient indices between the manually optimized plans and the KBP plans. The volume of PTV receiving prescription dose increased from 93.3 ± 3.2% to 99.5 ± 0.7% (P<0.001) when using KBP. High-dose spillage to surrounding normal tissues (V105%) showed no significant differences (2.1 ± 7.3 cc for manual plans to 1.2 ± 0.4 cc with KBP), and dosimetric outliers with large amounts of spillage were eliminated through the use of KBP. Incorporation of KBP models into the clinical trial setting may have a profound impact on the quality of trial results due to the increase in consistency and standardization of planning, especially for treatment sites or techniques that are non-standard. The KBP model will be made available on the Center for Innovation in Radiation Oncology website.