Invasive Nodal Staging May Not Reduce Regional and Distant Recurrence Rates for Patients Treated with SBRT for Inoperable Stage I NSCLC

Abstract

In patients receiving definitive stereotactic body radiation therapy (SBRT) for presumably node-negative, early-stage non-small cell lung cancer (NSCLC), many patients are staged with PET-CT alone. The role of invasive nodal staging with either bronchoscopy plus endobronchial ultrasound (EBUS) or mediastinoscopy in patients undergoing PET prior to definitive lung SBRT is uncertain. We sought to characterize the impact of nodal staging modality on clinical outcomes after SBRT for early NSCLC. Patients receiving definitive SBRT for T1-2N0 NSCLC that were determined to be node-negative by either PET plus invasive nodal staging (EBUS or mediastinoscopy) or PET alone were identified using a single-institution prospective registry. All patients received 3-5 fraction SBRT with a biologically effective dose (BED10) of ≥ 100 Gy. Patients who did not undergo pre-SBRT PET, received adjuvant systemic therapy, or who were treated with additional SBRT courses for synchronous or metachronous NSCLC were excluded from the current study. Multivariable logistic regression was performed to identify which variables were independently associated with invasive mediastinal staging. Variables evaluated included staging, age, gender, ethnicity, central versus peripheral location, stage, and histology. A total of 651 patients treated from 2005 – 2016 met the above inclusion criteria. Invasive nodal staging was performed in 15.2% of patients (n=99) with either EBUS (n= 78) or mediastinoscopy (n= 21). Median age at SBRT was 75.3 years (range, 49.3 – 88.8). Median follow up was 19.4 months, and median survival was 28.5 months for all patients. Factors predictive of increased likelihood to receive invasive nodal staging on multivariable analysis were young age (OR for increasing age 0.968; 95% CI 0.945 – 0.990), white race (OR for non-white 0.540; 0.304 = 0.958), female patients (OR 1.629; 95% CI 1.031 – 2.575), central location (OR 1.978; 95% CI 1.218 – 3.211) and squamous histology (OR 2.564; 95% CI 1.243 – 5.287). On multivariable analysis, nodal and/or distant failure was not significantly different between PET alone (crude failure rate, 23.6%) versus invasive nodal staging (25.4%, p=0.714) in this patient cohort. Most patients with early stage NSCLC treated with definitive SBRT did not undergo invasive nodal staging, and we identify several factors predictive of its use. There was no significant difference in nodal or distant failure based on type of nodal staging utilized.