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Dosimetric Comparison of IFSO and IMPT Methods in Scanning Beam Proton Therapy of Squamous Cell Carcinoma of The Anus

A Anand1*, J Lentz1, S Ito2, C Beltran3, M Bues1, B Kazemba2, J Archuleta1, T Sio1, W Rule1, C Hallemeier2, M Haddock2, J Ashman1, (1) Mayo Clinic Arizona, Phoenix, AZ, (2)Mayo Clinic, Rochester, MN, (3) Mayo Clinic, Jacksonville, FL.


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

Room: AAPM ePoster Library


To compare two separate dosimetric methods utilizing a split target technique of Individual Field Simultaneous Optimization (IFSO) versus a single target Multi-Field Optimization (IMPT) in scanning Proton beam therapy (sPBT) for squamous cell carcinoma of the anus.


At the time of this submission a set of 3 randomly selected retrospective cases from our clinic were used to prepare sPBT plans utilizing Eclipse Treatment Planning Software V 15.1. A novel IFSO technique utilizing beam specific split target volumes with scanning pencil beam proton technology was compared with conventionally planned single target IMPT method. A Lexicographic ordering of optimization was utilized in order to generate IFSO and IMPT plans with same penalties applied for the objective constraints. All plans were normalized to V95 for inter-comparison between the two methods.


Both plans computed with IFSO and IMPT provided adequate target coverage. IFSO method results in greater sparing of the healthy organs. Max doses for Large and Small Bowel showed no appreciable differences between the two methods, however large percentage difference in sparing of healthy tissues between the IFSO and IMPT methods ((IFSO/IMPT) %) was observed as listed below (difference in percent):
(Bladder: Dmean,average = 60%, V40, average: 22%); (Genitalia: Dmean, average: 68%); (Large Bowel: Dmean. average = 20%); (Small Bowel: Dmean, average = 45%); Both Methods were comparable in terms of sparing of the low dose Bone Marrow (V10, average: 3%).


A novel IFSO technique is a valuable tool to spare several healthy organs when treating squamous cell carcinoma of the anus with scanning beam proton therapy when compared with single target IMPT.


Protons, Treatment Planning, Treatment Techniques


TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

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