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Quantification of Potential and Clinical Improvement in Head and Neck IMRTOAR Sparing Using a Feasibility DVH Derived From a 3D High Gradient Dose Spread Model

D Fried

D Fried1*, M Kostich1 , B Nelms2 , B Chera1 , S Das1 , (1) University of North Carolina, Chapel Hill, NC, (2) Canis Lupis LLC, Merrimac, Wisconsin


SU-I-GPD-T-395 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Frequently planner/physician experience is relied upon to determine how much an organ-at-risk (OAR) can be spared. An algorithm that derives a Feasibility-DVH using a high gradient dose spread model removes this subjectivity and provides users with quantitative expectations for sparing. We hypothesize that this algorithm could facilitate reduction in dose to head and neck OARs.

Methods: Ten clinically delivered head and neck plans were re-planned emphasizing maximal sparing of the contralateral parotid gland, contralateral submandibular gland, and larynx while maintaining routine dosimetric objectives. The re-planner was blinded to the results of the clinical plan. The planner was then given the results from Sun Nuclear’s PlanIQ Feasibility-DVH analysis and developed an additional plan (IQ plan). OAR DVHs across the 3 plans were compared with what was deemed “impossible” by the Feasibility-DVH (Impossible-DVH). Feasibility-DVH was then implemented into our clinical planning workflow. The average difference between delivered and Impossible DVHs for the contralateral parotid and larynx were compared pre and post implementation for a single planner.

Results: The re-plans performed blinded to Feasibility-DVH achieved superior sparing of the contralateral parotid and larynx compared to the clinically delivered plans (contralateral submandibular gland remained relatively constant), but fell short of achieving the Impossible-DVH by an average of 2-7Gy. Using the PlanIQ Feasibility-DVH led to additional OAR sparing compared to both the re-plans and clinical plans and reduced the discrepancies from the Impossible-DVHs to an average of approximately 1Gy. Implementing Feasibility-DVH clinically led to a reduction in discrepancy from the Impossible-DVH of 5.8Gy and 7.2Gy for the contralateral parotid and larynx, respectively.

Conclusion: Both clinical treatment plans and blinded re-plans were found to sub-optimally spare OARs. Feasibility-DVH was able to aid planners in a clinical environment by generating treatment plans that push the limits of OAR sparing while maintaining routine clinical target coverage goals.

Funding Support, Disclosures, and Conflict of Interest: UNC Radiation Oncology Department has previously received research grant from Sun Nuclear Corp. However, none of the authors individually received funds from Sun Nuclear.

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