Imaging Features Associated With Disease Progression After Stereotactic Ablative Radiotherapy for Stage I Non-Small-Cell Lung Cancer

We retrospectively identified imaging-based biomarkers in 117 patients with stage I non small-cell lung cancer (NSCLC) treated with stereotactic ablative radiotherapy (SABR). Tumor size, contact with the mediastinal pleura, and maximum standard uptake value (SUVmax) significantly correlated with distant metastasis and were incorporated into a prognostic index that could be used to identify patients most likely to benefit from adjuvant systemic therapy following SABR. Introduction/Background: The aim of this study was to identify imaging-based predictors of progression in patients treated with SABR for stage I NSCLC. Patients and Methods: Between March 2003 and December 2012, 117 patients with stage I NSCLC meeting our study criteria were treated with SABR at Stanford University. Median follow-up was 17 months (range, 3-74 months) for all patients and 19 months for living patients (range, 3-74 months). Tumors were classified according to whether or not they contacted the pleura adjacent to the chest wall or mediastinum (MP), according to their maximum dimension based on computed tomography scans, and, for 102 patients who had archived pretreatment fluorine-18 fluorodeoxyglucose positron-emission tomography scans, according to SUVmax. Results: Ten patients (9%) developed local progression, 17 (15%) developed regional progression, and 19 (16%) developed distant metastasis. Two-year freedom from local progression, freedom from regional progression, and freedom from distant metastasis (FFDM) were 88%, 83%, and 83%, respectively. Overall survival was 70% at 2 years. FFDM was significantly associated with MP contact, maximum tumor dimension, and SUVmax, and these variables could be combined into an exploratory prognostic index that identified patients at highest risk for developing metastases. Conclusion: In our cohort, noninvasive, imaging-based features were associated with distant progression after SABR for early stage NSCLC. If validated, our prognostic index could allow identification of patients who might benefit from systemic therapy after SABR. Published by Elsevier Inc.