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Title: SU-F-T-221: An Assessment of the Potential for Improved Local Control of Skull- Base Chordomas Via Reduction of the Proton Beam Range Uncertainty

Abstract

Purpose: The beam range uncertainty presents a special challenge for proton therapy. Novel technologies currently under development offer strategies to reduce the range uncertainty [1,2]. This work quantifies the potential advantages that could be realized by such a reduction for dosimetrically challenging chordomas at the base of skull. Therapeutic improvement was assessed by evaluating tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP). Methods: Treatment plans were made for a modulated-scanned proton delivery technique using the Eclipse treatment planning system. The prescription dose was 7920 cGy to the CTV. Three different range uncertainty scenarios were considered: 5 mm (3.5% of the beam range + 1 mm, representing current clinical practice, “Curr”), 2 mm (1.3%), and 1 mm (0.7%). For each of 4 patients, 3 different PTVs were defined via uniform expansion of the CTV by the value of the range uncertainty. Tumor control probability (TCP) and normal tissue complication probabilities (NTCPs) for organs-at-risk (OARs) were calculated using the Lyman-Kutcher-Burman[3] formalism and published model parameters [ref Terahara[4], quantec S10, Burman Red Journal v21 pp 123]. Our plan optimization strategy was to achieve PTV close to prescription while maintaining OAR NTCP values at or better than the Curr plan. Results: Themore » average TCP values for the 5, 2, and 1 mm range uncertainty scenarios are 51%, 55% and 65%. The improvement in TCP for patients was between 4 and 30%, depending primarily on the proximity of the GTV to OAR. The average NTCPs for the brainstem and cord were about 4% and 1%, respectively, for all target margins. Conclusion: For base of skull chordomas, reduced target margins can substantially increase the TCP without increasing the NTCP. This work demonstrates the potential significance of a reduction in the range uncertainty for proton beams.« less

Authors:
; ; ; ; ; ;  [1]
  1. University of Pennsylvania, Philadelphia, PA (United States)
Publication Date:
OSTI Identifier:
22648838
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; NEOPLASMS; PLANNING; PROTON BEAMS; RADIATION DOSES; RADIOTHERAPY; TCP

Citation Formats

Muller, L, Soldner, A, Kirk, M, Fager, M, Solberg, T, Robert, L, and Dolney, D. SU-F-T-221: An Assessment of the Potential for Improved Local Control of Skull- Base Chordomas Via Reduction of the Proton Beam Range Uncertainty. United States: N. p., 2016. Web. doi:10.1118/1.4956360.
Muller, L, Soldner, A, Kirk, M, Fager, M, Solberg, T, Robert, L, & Dolney, D. SU-F-T-221: An Assessment of the Potential for Improved Local Control of Skull- Base Chordomas Via Reduction of the Proton Beam Range Uncertainty. United States. doi:10.1118/1.4956360.
Muller, L, Soldner, A, Kirk, M, Fager, M, Solberg, T, Robert, L, and Dolney, D. Wed . "SU-F-T-221: An Assessment of the Potential for Improved Local Control of Skull- Base Chordomas Via Reduction of the Proton Beam Range Uncertainty". United States. doi:10.1118/1.4956360.
@article{osti_22648838,
title = {SU-F-T-221: An Assessment of the Potential for Improved Local Control of Skull- Base Chordomas Via Reduction of the Proton Beam Range Uncertainty},
author = {Muller, L and Soldner, A and Kirk, M and Fager, M and Solberg, T and Robert, L and Dolney, D},
abstractNote = {Purpose: The beam range uncertainty presents a special challenge for proton therapy. Novel technologies currently under development offer strategies to reduce the range uncertainty [1,2]. This work quantifies the potential advantages that could be realized by such a reduction for dosimetrically challenging chordomas at the base of skull. Therapeutic improvement was assessed by evaluating tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP). Methods: Treatment plans were made for a modulated-scanned proton delivery technique using the Eclipse treatment planning system. The prescription dose was 7920 cGy to the CTV. Three different range uncertainty scenarios were considered: 5 mm (3.5% of the beam range + 1 mm, representing current clinical practice, “Curr”), 2 mm (1.3%), and 1 mm (0.7%). For each of 4 patients, 3 different PTVs were defined via uniform expansion of the CTV by the value of the range uncertainty. Tumor control probability (TCP) and normal tissue complication probabilities (NTCPs) for organs-at-risk (OARs) were calculated using the Lyman-Kutcher-Burman[3] formalism and published model parameters [ref Terahara[4], quantec S10, Burman Red Journal v21 pp 123]. Our plan optimization strategy was to achieve PTV close to prescription while maintaining OAR NTCP values at or better than the Curr plan. Results: The average TCP values for the 5, 2, and 1 mm range uncertainty scenarios are 51%, 55% and 65%. The improvement in TCP for patients was between 4 and 30%, depending primarily on the proximity of the GTV to OAR. The average NTCPs for the brainstem and cord were about 4% and 1%, respectively, for all target margins. Conclusion: For base of skull chordomas, reduced target margins can substantially increase the TCP without increasing the NTCP. This work demonstrates the potential significance of a reduction in the range uncertainty for proton beams.},
doi = {10.1118/1.4956360},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}