2833 - Tumor Control Probability Modeling of Pulmonary Metastases in Oligometastatic Head and Neck Squamous Cell Carcinoma Treated with Stereotactic Body Radiotherapy
Presenter(s)
A. Ruhle1,2, S. Vorbach3, F. Nägler1, A. A. Mohamed4, A. Rimner2, T. Weissmann5, J. Kaufmann6, K. M. Kraus7,8, K. Dehl9, S. Rogers10, A. Gawish11, J. N. Becker12, R. J. Klement13, R. Partl14, A. Wittig-Sauerwein15, O. Blanck16,17, P. Balermpas18, G. Subedi19,20, J. Grimm21, and F. Ehret22,23; 1Department of Radiation Oncology, University of Leipzig Medical Center, Leipzig, Germany, 2Department of Radiation Oncology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK), partner site DKTK-Freiburg, Freiburg, Germany, 3Department of Radiation Oncology, Medical University of Innsbruck, Innsbruck, Austria, 4Department of Radiation Oncology, RWTH Aachen University Hospital, Aachen, Aachen, Germany, 5Department of Radiation Oncology, University Hospital of Erlangen, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen, Germany, 6Department of Radiation Oncology, University Medical Center Mainz, Mainz, Germany, 7Department of Radiation Oncology, School of Medicine and Health and Klinikum rechts der Isar, Technical University of Munich (TUM), Munich, Germany, 8Institute of Radiation Medicine (IRM), Helmholtz Munich, German Research Center for Environmental Health (HMGU) GmbH, Neuherberg, Germany, 9Department of Radiation Oncology, University Hospital Hamburg-Eppendorf, Hamburg, Germany, 10Radiation Oncology Center Mittelland, Kantonsspital Aarau, Aarau, Switzerland, 11Department of Radiotherapy, University Medical Center Giessen-Marburg, Marburg, Germany, 12Department of Radiotherapy, Hannover Medical School, Hannover, Germany, 13Department of Radiotherapy and Radiation Oncology, Leopoldina Hospital Schweinfurt, Schweinfurt, Germany, 14Department of Radiation Oncology, Medical University of Graz, Graz, Austria, 15University Hospital Würzburg, Department of Radiation Oncology, Würzburg, Germany, 16Saphir Radiosurgery Center Frankfurt and Northern Germany, Kiel, Germany, 17Department of Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel, Germany, 18Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland, 19Department of Radiation Oncology, Wellstar Kennestone Hospital, Marietta, GA, 20Georgia Institute of Technology, Atlanta, GA, 21Wellstar Health System, Marietta, GA, 22German Cancer Consortium (DKTK), partner site Berlin, a partnership between DKFZ and Charité – Universitätsmedizin Berlin, Berlin, Germany, 23Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Radiation Oncology, Berlin, Germany, Berlin, Germany
Purpose/Objective(s): Local control rates for pulmonary metastases from head and neck squamous cell carcinoma (HNSCC) treated with stereotactic body radiotherapy (SBRT) vary substantially in the literature, likely due to differences in the doses applied and many other potential factors. This study aims to model and evaluate the local tumor control probability (TCP) for pulmonary metastases from oligometastatic HNSCC treated with SBRT, focusing on the potential dose dependence of outcomes.
Materials/Methods: We conducted an international, multicenter cohort study including 16 centers. This retrospective analysis focused on local control outcomes in patients with oligometastatic HNSCC who underwent SBRT for pulmonary metastases between January 2010 and December 2023. Time-dose-response models for local control at 1 and 3 years post-SBRT were developed. To form the time-dose-response model, data were stratified into four dose groups. Kaplan-Meier analysis was performed on each dose group separately, and the maximum likelihood parameter estimation was performed on the 1- and 3-year actuarial results.
Results: A total of 178 patients with 284 pulmonary HNSCC metastases were analyzed. The three most common dose prescriptions were 45 Gy in 3 fractions (n=70, 25%), 37.5 Gy in 3 fractions (n=24, 8%), and 72 Gy in 12 fractions (n=23, 8%). The median planning target volume (PTV) was 15 cc (IQR, 8-27 cc), and the median biologically effective dose (BED a/ß = 10 Gy) delivered at the PTV-encompassing isodose was 105 Gy (IQR, 84-113 Gy). Fifteen lesions (5.3%) developed local recurrence after a median time of 8 months (IQR, 1-10 months), and the median BED of recurring lesions was 89 Gy (IQR, 72-96 Gy). The 1-year and 3-year cumulative incidence of local failures was 5.5% (95% CI, 3.1-8.8%) and 6.0% (95% CI, 3.5-9.4%), respectively. The time-dose-response models for 1 year and 3 years demonstrated a dose-dependent effect. A BED of nearly 100 Gy at the PTV-encompassing isodose is necessary to achieve a 1-year local control of more than 95%. For a 1-year local control rate of 90%, a BED of more than 80 Gy is necessary. With BED doses below 80 Gy, the local control rates sharply decrease, with 50 Gy BED providing a local control of less than 70%. After 3 years, a BED of more than 110 Gy is necessary to achieve a local control rate of at least 95%. The corresponding doses to achieve control rates of 90% and 80% after 3 years are >90 and >70 Gy BED, respectively.
Conclusion: To the best of our knowledge, this is the first report of TCP models specifically for pulmonary metastases from HNSCC treated with SBRT. While SBRT achieves excellent local control rates, the developed time-dose-response models highlight the critical role of the BED prescribed to the PTV. Although prospective validation of these models is required, our findings suggest using a BED of at least 100 Gy to the PTV-encompassing isodose for pulmonary HNSCC metastases treated with SBRT.