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Author Underwood, Tracy ♦ Giantsoudi, Drosoula ♦ Moteabbed, Maryam ♦ Zietman, Anthony ♦ Efstathiou, Jason ♦ Paganetti, Harald ♦ Lu, Hsiao-Ming
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword RADIOLOGY AND NUCLEAR MEDICINE ♦ IN VIVO ♦ LET ♦ MONTE CARLO METHOD ♦ PROSTATE ♦ PROTON BEAMS ♦ RADIOTHERAPY ♦ RBE ♦ RECTUM ♦ SIMULATION ♦ VARIATIONS
Abstract Purpose: For prostate treatments, robust evidence regarding the superiority of either intensity modulated radiation therapy (IMRT) or proton therapy is currently lacking. In this study we investigated the circumstances under which proton therapy should be expected to outperform IMRT, particularly the proton beam orientations and relative biological effectiveness (RBE) assumptions. Methods and Materials: For 8 patients, 4 treatment planning strategies were considered: (A) IMRT; (B) passively scattered standard bilateral (SB) proton beams; (C) passively scattered anterior oblique (AO) proton beams, and (D) AO intensity modulated proton therapy (IMPT). For modalities (B)-(D) the dose and linear energy transfer (LET) distributions were simulated using the TOPAS Monte Carlo platform and RBE was calculated according to 3 different models. Results: Assuming a fixed RBE of 1.1, our implementation of IMRT outperformed SB proton therapy across most normal tissue metrics. For the scattered AO proton plans, application of the variable RBE models resulted in substantial hotspots in rectal RBE weighted dose. For AO IMPT, it was typically not possible to find a plan that simultaneously met the tumor and rectal constraints for both fixed and variable RBE models. Conclusion: If either a fixed RBE of 1.1 or a variable RBE model could be validated in vivo, then it would always be possible to use AO IMPT to dose-boost the prostate and improve normal tissue sparing relative to IMRT. For a cohort without rectum spacer gels, this study (1) underlines the importance of resolving the question of proton RBE within the framework of an IMRT versus proton debate for the prostate and (2) highlights that without further LET/RBE model validation, great care must be taken if AO proton fields are to be considered for prostate treatments.
ISSN 03603016
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-05-01
Publisher Place United States
Journal International Journal of Radiation Oncology, Biology and Physics
Volume Number 95
Issue Number 1


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