TY - JOUR
T1 - SABR for Skull Base Malignancies
T2 - A Systematic Analysis of Set-Up and Positioning Accuracy
AU - Mesko, Shane
AU - Wang, He
AU - Tung, Samuel
AU - Wang, Congjun
AU - Pasalic, Dario
AU - Ning, Matthew S.
AU - Pezzi, Todd A.
AU - Moreno, Amy C.
AU - Reddy, Jay P.
AU - Garden, Adam S.
AU - Rosenthal, David I.
AU - Gunn, G. Brandon
AU - Frank, Steven J.
AU - Fuller, Clifton D.
AU - Morrison, William
AU - Su, Shirley Y.
AU - Hanna, Ehab
AU - Phan, Jack
N1 - Funding Information:
Disclosures: Dr Mesko has a consulting agreement with Oscar Health care. Dr Rosenthal serves on the scientific advisory board for Merck. Dr Phan serves on the scientific advisor board for Cyberknife for Accuray, Inc. Dr Frank reports personal fees from Varian, grants and personal fees from C4 Imaging, grants from Eli Lilly and Elekta, grants and personal fees from Hitachi, other support from Breakthrough Chronic Care, and personal fees from Boston Scientific and the National Comprehensive Cancer Network, all of which are outside the submitted work. Dr Fuller has received grants (unrelated to the present work) from GE Health care, Elekta AB, National Science Foundation (NSF 1557559), National Institutes of Health (NIH 1R56DE025248-01, 1R25EB025787-01, 5R01CA214825-02; 5R01CA225190-02; 5R01CA218148-02, CA088084), the Sabin Family Foundation, and an MD Anderson Institutional Research Grant. Dr Fuller has received payments for lectures from the University of Texas Health Science Center San Antonio and from Elekta AB. Dr Fuller has received royalties from Demos Medical Publishing and travel/accommodations/meeting expenses from Oregon Health & Science University, Greater Baltimore Medical Center, University of Illinois, Elekta AB, and the Translational Research Institute Australia.
Funding Information:
Sources of support: This work had no specific funding. Disclosures: Dr Mesko has a consulting agreement with Oscar Health care. Dr Rosenthal serves on the scientific advisory board for Merck. Dr Phan serves on the scientific advisor board for Cyberknife for Accuray, Inc. Dr Frank reports personal fees from Varian, grants and personal fees from C4 Imaging, grants from Eli Lilly and Elekta, grants and personal fees from Hitachi, other support from Breakthrough Chronic Care, and personal fees from Boston Scientific and the National Comprehensive Cancer Network, all of which are outside the submitted work. Dr Fuller has received grants (unrelated to the present work) from GE Health care, Elekta AB, National Science Foundation (NSF 1557559), National Institutes of Health (NIH 1R56DE025248-01, 1R25EB025787-01, 5R01CA214825-02; 5R01CA225190-02; 5R01CA218148-02, CA088084), the Sabin Family Foundation, and an MD Anderson Institutional Research Grant. Dr Fuller has received payments for lectures from the University of Texas Health Science Center San Antonio and from Elekta AB. Dr Fuller has received royalties from Demos Medical Publishing and travel/accommodations/meeting expenses from Oregon Health & Science University, Greater Baltimore Medical Center, University of Illinois, Elekta AB, and the Translational Research Institute Australia.
Publisher Copyright:
© 2020
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Purpose: Here we provide an analysis of the set-up and positioning accuracy of SABR for skull base malignancies to evaluate the use of site- or axis-specific margins to reduce field size. Methods and Materials: Data were prospectively collected on 63 patients who received 304 fractions of SABR for recurrent/previously irradiated skull base tumors. Using our custom cushion-mask-bite-block immobilization system combined with ExacTrac x-ray and cone beam computed tomography (CBCT), set-up, residual, CBCT-positioning agreement, and intrafractional errors were measured. The resulting planning target volume (PTV) margins were estimated across 4 skull base subsites: anterior (group 1), central (group 2), posterolateral (group 3), and skull base–associated sites (eg, nasopharynx/retropharyngeal, cervical vertebrae 1-2, occiput) (group 4). Results: On initial set-up, 66% of treatment courses required shifts of >2 mm or >2°, necessitating 4.9 mm PTV margins without image guidance. After correction, only 6 of 304 treatment sessions had residual errors >1 mm. CBCT-ExacTrac agreement was ≤1 mm in 89.1% of treatments and ≤1.5 mm in all but 1 session. Group 4 showed a higher rate of >1 mm or >1° CBCT-positioning differences compared with other groups (24.5% vs 7.8%; P =.0001), and the greatest variations occurred in the craniocaudal translational and the pitch rotational axes. Overall calculated PTV margins (based on intrafractional error) were 1.5 mm across subsites except for group 4, which required 2.0 mm margins. Conclusions: The use of 2.0 mm PTV margins for skull base SABR appears feasible using ExacTrac x-ray as the sole imaging modality for most subsites. However, PTVs were not uniformly equal, and the use of a site-specific nonuniform margin reduction to optimize critical-organ dose sparing may be feasible for select cases. These findings warrant clinical investigation.
AB - Purpose: Here we provide an analysis of the set-up and positioning accuracy of SABR for skull base malignancies to evaluate the use of site- or axis-specific margins to reduce field size. Methods and Materials: Data were prospectively collected on 63 patients who received 304 fractions of SABR for recurrent/previously irradiated skull base tumors. Using our custom cushion-mask-bite-block immobilization system combined with ExacTrac x-ray and cone beam computed tomography (CBCT), set-up, residual, CBCT-positioning agreement, and intrafractional errors were measured. The resulting planning target volume (PTV) margins were estimated across 4 skull base subsites: anterior (group 1), central (group 2), posterolateral (group 3), and skull base–associated sites (eg, nasopharynx/retropharyngeal, cervical vertebrae 1-2, occiput) (group 4). Results: On initial set-up, 66% of treatment courses required shifts of >2 mm or >2°, necessitating 4.9 mm PTV margins without image guidance. After correction, only 6 of 304 treatment sessions had residual errors >1 mm. CBCT-ExacTrac agreement was ≤1 mm in 89.1% of treatments and ≤1.5 mm in all but 1 session. Group 4 showed a higher rate of >1 mm or >1° CBCT-positioning differences compared with other groups (24.5% vs 7.8%; P =.0001), and the greatest variations occurred in the craniocaudal translational and the pitch rotational axes. Overall calculated PTV margins (based on intrafractional error) were 1.5 mm across subsites except for group 4, which required 2.0 mm margins. Conclusions: The use of 2.0 mm PTV margins for skull base SABR appears feasible using ExacTrac x-ray as the sole imaging modality for most subsites. However, PTVs were not uniformly equal, and the use of a site-specific nonuniform margin reduction to optimize critical-organ dose sparing may be feasible for select cases. These findings warrant clinical investigation.
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U2 - 10.1016/j.prro.2020.02.016
DO - 10.1016/j.prro.2020.02.016
M3 - Article
C2 - 32240823
AN - SCOPUS:85087991973
SN - 1879-8500
VL - 10
SP - 363
EP - 371
JO - Practical radiation oncology
JF - Practical radiation oncology
IS - 5
ER -