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Photon Vs Proton Therapy Comparison of Clinically Significant Dosimetric Parameters That Lead to Radiation Induced Toxicity in Lung SBRT

K Wijesooriya1*, B Neal2, J Colen3, E Aliotta4, S Katugampola5, C Hodge6, J Larner7, (1) University of Virginia Health Systems, Charlottesville, VA, (2) ProCure Treatment Center, Hillsborough, NJ, (3) University Of Virginia Health Systems, ,,(4) University of Virginia, Charlottesville, VA, (5) University Of Virginia, ,,(6) University Of Virginia, ,,(7) University Of Virginia Health Systems,


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: induced toxicities during lung SBRT, such as cardiovascular disease, radiation pneumonitis, and immune suppression could have a negative impact on overall survival. We compared dosimetric parameters relevant to these toxicities between protons, and photons within RTOG 0813 and 0915 criteria.

Methods: analyzed 87 patients who received lung SBRT in our institution. For each patient the Dmax, V25 for great vessels; V5, V25, mean dose for heart; V5, V10, V15, V20 for total lung – ITV were recorded. We utilized an in-house model to obtain the above mentioned static organ doses as well as the overall immune suppression per given plan using a blood flow simulation model combined with an immune cell kill model and pre-treatment immune values.

Results: vessel maximum doses from photon plans range between 0 – 60 Gy with a mean values varying between 16.7-21.7 Gy, while proton plans great vessel maximum doses range between 0-55Gy with mean values varying between 5.2-8.9 Gy. Mean heart dose from photon plans vary between 0 -8 (mean =2.2) Gy while the mean heart dose from proton plans vary between 0-1.5 (mean = 0.1) Gy. V5 of total lung-ITV from photon plans has the largest variation with a mean of 266.8 cc for protons, and a mean of 683.4 cc for photons. Mean V20 of total lung-ITV is 180.4cc for photons, and 106.3cc for protons. Our re-planning study has demonstrated significant improvements to photon based lung SBRT plans to reduce radiation therapy related toxicity.

Conclusion: a handful of patients had great vessel dose-tolerance limit of Dmax > 52.5 Gy with photons that is shown to give a 1.2% risk of grade 3-5 toxicity. V20 for total lung –ITV that lead to radiation pneumonitis, and Dmax for great vessels are comparable between proton and photon plans with stringent planning constraints.




TH- External Beam- Photons: extracranial stereotactic/SBRT

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