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Outcomes After Stereotactic Ablative Radiotherapy (SABR) of Early Stage Non-Small Cell Lung Cancers Without Biopsy Proven Disease

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Purpose: SABR has become the standard of care for inoperable early stage non-small cell lung cancer. Many patients are unable to safely receive a biopsy given poor pulmonary function with underlying emphysema and thus are empirically treated with radiotherapy. This study was performed to evaluate the efficacy and safety of definitive SABR in this population.

Methods: 69 patients were analyzed with a median follow up of 18 months. Patient, tumor, radiation doses, pulmonary function tests (including subgroups with FEV1 < 1.0 L, FEV1 < 1.5 L, FEV1 < 30%, and FEV1 < 35%) and toxicity (acute ≤ 90 days and late > 90 days) were analyzed to find associations between overall survival (OS) on Kaplan-Meier log-rank testing and differences in the patient populations with Chi- Square and Mann-Whitney U tests.

Results: The median age was 71. Sixty two tumors were peripheral (88.6%). There were 4 local recurrences (5.7%), 10 regional (different lobe and nodal) failures (14.29%), 15 distant metastases (21.4%) and a median survival of 17 months. There were differences in OS based on operability status (P=0.031), acute toxicity (P=0.000), and acute grade 2 toxicity (P=0.003). Significant factors for differences in distribution among patients with and without acute toxicity were O2 dependence (P=0.047), long term toxicity (P=0.000), and long term grade 2 toxicity (P=0.000). In the acute grade 2 toxicity analysis, O2 dependence (P=0.003), central vs peripheral location (P=0.000), new O2 requirement (P=0.022), long term toxicity (P=0.004), and long term grade 2 toxicity P=0.010) were significant. There were no significant differences based on pulmonary function testing (FEV1, FVC, or DLCO) or the analyzed PFT subgroups.

Conclusion: Operability and acute toxicity are associated with differences in OS in those patients undergoing empiric SABR. O2 dependence prior to treatment and not PFT parameters were associated with acute toxicities.

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