Survival outcomes of stage I small cell lung cancer (SCLC) treated with stereotactic body radiation therapy (SBRT) versus external beam radiation therapy (EBRT): An NCDB analysis.

Abstract

e20638 Background: Patients with stage I (T1/T2a, N0) SCLC have a 5-year survival of 48% after surgical resection. Unfortunately, 70% of limited stage patients are inoperable and thus reliant on definitive radiation. The use of SBRT has increased 16-fold from 2004-2013 with continued widespread acceptance due to its safety and projected efficacy; however, there is no category one evidence to support this practice. Currently NCCN guidelines cite experience of SBRT in 117 patients from two studies. The impact of SBRT versus EBRT with or without chemotherapy is not yet well defined and requires more evidence to influence treatment decisions. Methods: We used National Cancer Database (NCDB) to identify 4,012 patients with clinical stage I SCLC treated with surgery, or EBRT with chemotherapy, or SBRT with or without chemotherapy from 2011 to 2020. The primary outcome analyzed was overall survival (OS). Secondary analyses evaluated differences amongst age, gender, race, institution, and Charlson Comorbidity Index (CCI). Kaplan-Meier (KM) plots were used to examine survival outcomes and descriptive analysis was performed to examine the characteristics of clinical variables by the different treatment modalities. Cox regression analysis was used to identify factors associated with OS. Results: The utilization of surgery and SBRT in stage I SCLC has increased over the last fifteen years. As of 2020, SBRT volume has increased 657-fold and is combined with chemotherapy in more than 50% of cases. From 2010-2019, those who were treated with surgery-based therapy had a survival advantage (HR 0.64 95%CI 0.58-0.71, p < 0.01) compared to multimodality radiotherapy techniques. For those treated with definitive radiation, there was no significant difference between EBRT with chemotherapy and SBRT with or without chemotherapy (HR 1.11 95%CI 0.97-1.28, p = 0.135). Patients treated with SBRT alone experienced a significantly shorter median OS of 20.4 months compared to those who received SBRT with chemotherapy (median OS 34.3 months, HR 1.74 95%CI 1.38-2.20, p < 0.01). Multivariate analysis revealed better OS for patients under the age of 64 (HR 0.51 95%CI 0.44-0.58, p <0.01) and those with lower CCI (CCI 0, HR 0.82 95%CI 0.70-0.90, p< 0.01); worse OS for males (HR 1.26 95%CI 1.16-1.37, p < 0.01); and no difference between academic or non-academic institutions (HR 0.92 95%CI 0.84-1.01, p= 0.094), white versus black (HR 0.84 95%CI 0.71-1.00, p = 0.054) or non-white patients (HR 1.06 95%CI 0.75-1.50, p = 0.736). Conclusions: Our preliminary results suggest surgery-based multimodality therapy is associated with a higher survival for medically operable patients. There was no survival advantage of EBRT with chemotherapy compared to SBRT especially when chemotherapy is given. Further statistical analysis is underway to confirm these trends and survival differences.