2110 - Definitions of Local Control after Stereotactic Body Radiation Therapy for Early-Stage Lung Cancer: A Systematic Review of the Literature

N. Nourmohammadi¹, C. Kashani², J. Nikitas², T. Oughourlian², J. D. Bradley³, M. Guckenberger⁴, S. Siva⁵, D. A. Palma⁶, S. S. Yom⁷, S. Senan⁸, and D. Moghanaki⁹; ¹1000 W. Carson Street, Torrance, CA, ²Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, ³Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, ⁴Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland, ⁵Peter MacCallum Cancer Centre, Melbourne, VIC, Australia, ⁶London Health Sciences Centre, London, ON, Canada, ⁷University of California San Francisco, San Francisco, CA, ⁸Amsterdam UMC, Amsterdam, Netherlands, ⁹VA Greater Los Angeles Healthcare System, Los Angeles, CA

Purpose/Objective(s): Definitions of local control after stereotactic body radiation therapy (SBRT) are not currently standardized and include determinations of relapse in the primary tumor, same lobe, ipsilateral lung, and/or regional nodes. Furthermore, radiologic and metabolic features used to distinguish primary tumor control from relapse are generally not validated and may contribute to varying determinations. We systematically reviewed the methods stated in peer-reviewed articles reporting local control rates after lung SBRT and investigated trends over time. Materials/

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline was used to identify, appraise, and synthesize articles published in PubMed reporting local control rates after lung SBRT from 2006-2023. Searched abstracts were evaluated to exclude reviews, reports lacking disease-control determinations, and abstracts not written in English. Remaining articles were considered eligible for analysis and individually reviewed to categorize reported local control definitions by the anatomic site(s) and criteria(s) used to distinguish local control from relapse.

Results: 155 peer-reviewed articles were reviewed and 114 were eligible for analysis. Local control determinations were termed “local control,” “local failure,” “local recurrence,” and “primary tumor control (or failure)” in 39%, 32%, 24%, and 4% of studies, respectively. Anatomic sites used for evaluations of local control relied upon primary tumor site, same lobe, ipsilateral lung, and regional nodes in 68%, 11%, 4%, and 2%, respectively; 15% did not specify an anatomic location. There was no change in the percentage of studies specifying primary tumor control over time (p=0.45). Local control determinations were reported in 94% of studies and relied on 12 different criteria, including specific imaging modalities (computed tomography [CT] or positron emission tomography [PET]), minimum growth (serial growth, Response Evaluation Criteria in Solid Tumors [RECIST], or 20-50% size increase), period of growth (2-36 months or serial growth), or histopathological confirmation in 28%, 31%, 18%, and 1%, respectively.

Conclusion: There is substantial variability in definitions reported in the peer-reviewed literature to measure local control rates after lung SBRT. Definitions often include relapse in the same lobe, ipsilateral lung, and regional nodes. Furthermore, various parameters subject to interpretation bias are used for local control determinations. There is a need to standardize post-SBRT local control definitions for greater accuracy in reporting primary tumor control rates and to facilitate more robust comparisons between studies.