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Mediastinal Staging for SBRT in Early NSCLC: Should it be Stratified by Tumor Size and Location?

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Background: Stereotactic body radiotherapy (SBRT) is standard treatment for inoperable early-stage nonsmall cell lung cancer (NSCLC) . American College of Chest Physicians (ACCP) favors non-invasive mediastinal staging for peripheral Stage IA tumors for surgical patients. However, mediastinal staging guidelines for SBRT are still elusive and benefit of endobronchial ultrasound guided transbronchial needle biopsy (EBUS/ TBNA) in addition to positron emission tomographycomputed tomography (PET/CT) remains undefined for small peripheral NSCLC.

Purppose: To evaluate our SBRT- EBUS program by comparing survival and patterns of failure in SBRT patients staged with PET/CT and EBUS/TBNA vs. PET/ CT only for < 4cm peripheral NSCLC.

Methods: Patients with early NSCLC treated with Cyberknife (CK) from October 2010 to December 2016 were queried. Those treated definitively for single, < 4cm peripheral tumors were included. Local, regional, distant recurrences and survival outcomes were compared between patients staged with PET/CT and EBUS/TBNA vs. PET/CT only, using competing risk analysis.

Results: One hundred and fifty nine patients were treated during the study period. Mediastinum was staged using PET/CT only till 2013. Ninety one patients (mean age 69 years [64-78 years]; 99 [99%] males) had peripheral single tumors of < 4 cm2. Seventy two were staged with EBUS/TBNA and PET/CT( group I) and 19 with PET/CT only (group II). Patient ,tumor and treatment characteristics, except race, were not different. At median follow-up of 5.39 years, group I vs. group II pattern of recurrence was ;any recurrence 36.1%vs.36.1%, P=0.95; local recurrence 13.9%vs.21.1%, P=0.48; regional recurrence 13.9% vs.21.1%, P=0.48; distant recurrence 25% vs.15.8%, P=0.55 respectively .Median OS for group I and group II was 2.95 years (2.37-3.80 years, 95%CI ) and 4 years (2.01-7.08 years 95%CI); P=0.54 respectively.

Conclusion: Survival outcomes and pattern of failure were not different based on type of mediastinal staging. EBUS/TBNA use can be safely stratified based on tumor location and size in this population. Therefore, for patients with single, < 4 cm2, peripheral NSCLC, non-invasive mediastinal staging with PET/CT may suffice for definitive SBRT. Future prospective studies are needed to validate our findings.

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