Head and Neck Cancer

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MO_36_2855 - Radiation Dose-Volume Tolerance for Hypofractionated Head-and-Neck Retreatments: A Report from the HyTEC Normal Tissue Complication Probability Working Group for Carotid Blowout Syndrome

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Radiation Dose-Volume Tolerance for Hypofractionated Head-and-Neck Retreatments: A Report from the HyTEC Normal Tissue Complication Probability Working Group for Carotid Blowout Syndrome
J. A. Vargo1, J. Grimm2, P. Mavroidis3, V. Moiseenko4, S. Jain5, J. J. Caudell6, D. A. Clump II7, S. K. Das8, L. B. Marks9, E. G. Moros10, Y. Vinogradskiy11, J. Xue12, E. D. Yorke13, and D. E. Heron14; 1Department of Radiation Oncology, West Virginia University, Morgantown, WV, 2Johns Hopkins University, Baltimore, MD, 3University of North Carolina at Chapel Hill, Chapel Hill, NC, 4University of California, San Diego, La Jolla, CA, 5VA Hospital, Tampa, FL, 6H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, 7UPMC Hillman Cancer Center, Department of Radiation Oncology, Pittsburgh, PA, 8Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC, 9Lineberger Comprehensive Cancer Center, University of North Carolina Hospitals, Chapel Hill, NC, 10H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, 11Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, CO, 12Department of Radiation Oncology, NYU Langone Health, New York, NY, 13Memorial Sloan Kettering Cancer Center, New York, NY, 14UPMC Hillman Cancer Center, Pittsburgh, PA

Purpose/Objective(s): While a growing body of data continues to evolve supporting the use of Stereotactic Body Radiation Therapy (SBRT) in recurrent head-and-neck cancer, quantitative guidelines for normal tissue constraints are lacking. The objective of the AAPM Working Group on Biological Effects of Hypofractionated Radiation Therapy/SBRT (HyTEC) is to critically summarize the published data in order to help guide clinical practice. Herein, we present Normal Tissue Complication Probability (NTCP) data for carotid blowout syndrome (CBS), hypothesizing that dose-volume constraints formed from existing literature for carotid dose can help guide clinical practice.

Materials/Methods: A PubMed search in April 2015 for “stereotactic AND neck AND radiation” resulted in 293 articles. The abstracts were searched for peer reviewed publications containing SBRT re-treatment in the head and neck region. Six candidate articles were identified and examined using the Qualitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) review forms adapted for SBRT. The median values for the maximum dose to the carotid artery (DMax) reported in the literature for CBS were replicated using maximum likelihood parameter estimation of the logistic model. The median values for DMax were then simulated into repeat binary outcomes and the 95% confidence intervals (95%CI) generated via the profile likelihood method.

Results: Doses from 268 cases from the 6 publications were selected with the re-irradiation DMax to the carotid artery ranging from 2.5-59.0 Gy in a median of 5 fractions. The fitted logistic model parameters for DMax to carotid artery were TD50=42.1Gy, γ50= 1.9766 (γ50=k/4), where TD50 is the tolerance dose, and γ50 and k are slope parameters. The 5-fraction equivalents for the DMax to the carotid artery from SBRT within the model that correlated to an estimated 2%, 5%, and 10% risk levels for CBS were 21.3 Gy (95%CI: 14.1-25.8), 26.4 Gy (95%CI: 21.7-29.6), and 30.4 Gy (95%CI: 27.3-33.0), respectively. Only 1 event of CBS occurred with DMax <30Gy in 5 fractions. The aggregate dose response curve becomes more steep in the vicinity of doses exceeding 30 Gy in 5 fractions.

Conclusion: The DMax to the carotid artery correlates with risks of CBS. Based on this model, we recommend restricting the volume of carotid receiving >30Gy in 5 fractions as much as possible without compromising tumor control, at the same time recognizing that recurrent head-and-neck cancer patients are 4-5 times more likely to die of uncontrolled disease than a complication of re-irradiation and the model does not take into account inter-fraction interval wherein treating every-other-day has a big effect on CBS risks. Updated and additional models will be presented.

Author Disclosure: J. Vargo: Speaker's Bureau; BrainLab. J. Grimm: Employee; Academic Urology. Patent/License Fees/Copyright; DiversiLabs, LLC. Co-Chair; AAPM SBRT Working Group. P. Mavroidis: None. S. Jain: None. D.A. Clump: None. S.K. Das: None. Y. Vinogradskiy: None. J. Xue: None. E.D. Yorke: Co-chair of WGSBRT; AAPM. Vice-chair of Task Group 100; AAPM. D.E. Heron: No personal compensation; Accuray Exchange in Radiation Oncology. Partnership; Cancer Treatment Services International. Vice Chairman of Clinical Affairs; University of Pittsburgh School of Medicine. Director of Radiation Services; UPMC CancerCenter.

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MO_36_2855 - Radiation Dose-Volume Tolerance for Hypofractionated Head-and-Neck Retreatments: A Report from the HyTEC Normal Tissue Complication Probability Working Group for Carotid Blowout Syndrome



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