Abstract
PurposeOur study reports the clinical outcomes of patients treated with 5-mm isotropic margin, fiducial-guided stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC). We also sought to assess the effect of histological subtype on local control.MethodsWe retrospectively reviewed the charts of all patients treated with SBRT for NSCLC between 2007 and 2017 at our institution. All patients who had implanted fiducial markers, planning target volume (PTV) margins of 5 mm or less, early stage disease (T1-T2, N0), and at least one follow-up CT were included in this analysis. Estimates of local control were generated using the Kaplan-Meier method, and differences between survival curves were assessed using the log-rank test.ResultsA total of 152 patients met the inclusion criteria for this analysis, with a median follow-up of 27.9 months. Patients received 54 Gy in three fractions for peripheral tumors and 48-52.5 Gy in four to five fractions for central tumors. NSCLC histology was adenocarcinoma in 69 (45.4%) cases, squamous cell carcinoma in 65 (42.8%) cases, and other or non-subtyped in 18 (11.8%) cases. Across the entire cohort, the two-year estimate of local control was 95.1%. When histology was considered, the two-year estimate of local control among patients with adenocarcinoma was 95.6% as compared with 85.0% for patients with other subtypes (p=0.044).ConclusionsFiducial-guided, isotropic 5-mm PTV margin for thoracic SBRT did not compromise local control compared with historical standards. In this series, patients with adenocarcinoma experienced improved local control compared with squamous cell carcinoma.
Highlights
Stereotactic body radiation therapy (SBRT) is a rapidly evolving radiation therapy technique that is showing promising results for the treatment of early stage non-small cell lung cancer (NSCLC)
We retrospectively reviewed the charts of all patients treated with SBRT for NSCLC between 2007 and 2017 at our institution
The two-year estimate of local control among patients with adenocarcinoma was 95.6% as compared with 85.0% for patients with other subtypes (p=0.044)
Summary
Stereotactic body radiation therapy (SBRT) is a rapidly evolving radiation therapy technique that is showing promising results for the treatment of early stage non-small cell lung cancer (NSCLC). SBRT is typically used for the treatment of patients who refuse surgical resection or have comorbidities rendering them poor surgical candidates [1]. Lung SBRT techniques used large internal target volume (ITV) margins with treatment delivered over the entire respiratory cycle [5]. Larger target volume expansions result in increased radiation exposure to normal lung parenchyma. We used a combination of respiratory-gated treatment delivery and fiducial guidance in order to reduce both ITV and planning target volume (PTV) margins and normal lung dose exposure. The ability to gate treatment delivery to a window around endexpiration allows for a significant reduction in ITV size [6].
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