N. K. Malik1, M. K. Farrugia2, H. Yu2, K. Wang2, D. Neimanis2, S. J. Ma3, and A. K. Singh1; 1Department of Radiation Medicine, Roswell Park Comprehensive Cancer Center, Buffalo, NY, 2Roswell Park Comprehensive Cancer Center, Buffalo, NY, 3Ohio State University, columbus, OH
Purpose/Objective(s): The use of stereotactic body radiation (SBRT) for thoracic malignancies for centrally located tumors can be associated with a high risk of treatment related mortality. To date, the optimal radiotherapeutic regimen for these patients remains unclear. We conducted a single arm prospective clinical trial to assess the safety and toxicity of single fraction SBRT for centrally located lung tumors. Materials/
Methods: Eligibility criteria included eastern cooperative oncology group (ECOG) performance status 0-2 with stage T1-3N0M0(= 6 cm), non-small cell lung cancer (NSCLC), and central tumor location, defined as tumors located within 2 cm in all directions of any mediastinal critical structures, including the proximal bronchial tree (PBT), esophagus, heart, brachial plexus, major vessels, spinal cord, phrenic nerve, and recurrent laryngeal nerve, as defined by the International Association for the Study of Lung Cancer (IASLC). A total of 30 patients were enrolled. Total dose delivered was 27 Gy in a single fraction. Sparing critical organs and meeting their dose-volume limits took precedence over planning target volume (PTV) coverage. PTV was cropped out of the critical organs of interest as necessary until the critical organ dose-volume limits were met. Minimum PTV coverage was 60% of the prescription dose. Adverse event rates were assessed using CTCAE version 4.0. Secondary endpoints included overall survival (OS) and local control (LC) which were calculated using Kaplan-Meier estimates. Results: Between February 2022 and October 2024, 30 patients were enrolled at a single US academic institution. The median follow-up was 12.7 months (range: 2.8-24.6). The median age was 78.9 years (range): 57.0-87.7), 17 (56.7%) were female, 20 (66.7%) were T1, 6 (20.0%) T2 and 3 (10.0%) T3. Among these patients, 14 (47%) were classified as central due to proximity to the PBT whereas 9 (30%) due to proximity to the mediastinal structures. In 7 (23%) patients, tumor was close to both the PBT and mediastinal structures. All patients were assigned a dose of 27 Gy in one fraction. No patients experienced G3-5 adverse events related to treatment. One patient experienced a grade 2 adverse event of back pain, whereas four patients experienced grade 1 fatigue. At the time of evaluation, LC was 97% and the estimated 1-year OS was 85% (95% Confidence Interval 69-93%). Conclusion: 27 Gy in a single fraction, planned and delivered with prioritization of critical organs and with pre-defined criteria for acceptable PTV coverage results in excellent tumor control with no grade 3-5 adverse events. A single fraction of SBRT can be as safe and effective as multiple doses of radiation in patients with central non-small cell lung cancer.
