Stereotactic body radiotherapy for central lung tumors: Finding the balance between safety and efficacy in the "no fly" zone

Abstract

Background: Stereotactic body radiotherapy (SBRT) has emerged as a highly effective technique to treat medically inoperable non-small cell lung cancer (NSCLC). Doses must be chosen carefully when treating central lesions because of the potential for significant toxicity. This study reviews the outcomes of a cohort of patients with central lung tumors treated with SBRT.

Methods: We identified 18 patients (12 women, 6 men) with central lesions that were treated with SBRT at our institution. Overall survival and local, regional, and distant control rates were assessed by Kaplan-Meier methodology. Correlations with outcomes were determined by multivariate analysis via Cox regression models.

Results: Eighty-nine percent of patients had a pathological diagnosis of NSCLC. The median dose to the planning target volume was 40 Gy (range: 30-50) in five fractions, yielding a median biologic equivalent dose (BED₁₀ ) of 72 (range: 48-100). The median planning target volume was 34 cc (range: 13.3-89). Local control was 87% at one year. Median overall survival was 45 months, with a two-year rate of 61%. The two-year regional control rate was 87%. BED₁₀ > 72 predicted improved progression-free survival, with one-year rates of 100% versus 40% with increased BED (P = 0.012). No grade 3 or higher acute or late toxicity was observed.

Conclusions: Lung SBRT to central lesions is safe and effective when using five fraction regimens. BED₁₀ < 72 predicted disease progression, highlighting the importance of choosing an effective dose fractionation scheme, which must in turn be balanced with potential toxicity.

Keywords: Lung cancer; radiation; stereotactic body radiotherapy.