TU‐C‐17A‐09: Multi‐Case Knowledge‐Based IMRT Treatment Planning in Head and Neck Cancer: Are Six Heads Better Than One?

Abstract

Purpose:HNC IMRT treatment planning is a challenging process that relies heavily on the planner’s experience. Previously, we used the single, best match from a library of manually planned cases to semi‐automatically generate IMRT plans for a new patient. The current multi‐case Knowledge Based Radiation Therapy (MC‐KBRT) study utilized different matching cases for each of six individual organs‐at‐risk (OARs), then combined those six cases to create the new treatment plan.Methods:From a database of 103 patient plans created by experienced planners, MC‐KBRT plans were created for 40 (17 unilateral and 23 bilateral) HNC “query” patients. For each case, 2D beam’s‐eye‐view images were used to find similar geometric “match” patients separately for each of 6 OARs. Dose distributions for each OAR from the 6 matching cases were combined and then warped to suit the query case’s geometry. The dose‐volume constraints were used to create the new query treatment plan without the need for human decision‐making throughout the IMRT optimization. The optimized MC‐KBRT plans were compared against the clinically approved plans and Version 1 (original KBRT) using the dose metrics: mean, median, and maximum (brainstem and cord+5mm) doses.Results:Compared to Version 1, MC‐KBRT had no significant reduction of the dose to any of the OARs in either unilateral/bilateral cases. Compared to the manually‐planned unilateral cases, there was significant reduction of the oral cavity mean/median dose (>2Gy) at the expense of the contralateral parotid. Compared to the manually‐planned bilateral cases, reduction of dose was significant in the ipsilateral parotid, larynx, and oral cavity (>3Gy mean/median) while maintaining PTV coverage.Conclusion:MC‐KBRT planning in head and neck cancer generates IMRT plans with equivalent dose sparing to manually created plans. MC‐KBRT using multiple case matches does not show significant dose reduction compared to using a single match case with dose warping.