Location Matters: Stage I Non-Small-cell Carcinomas of the Lower Lobes Treated With Stereotactic Body Radiation Therapy Are Associated With Poor Outcomes

Abstract

Introduction: The lung is a heterogeneous organ with relative overperfusion of the lung bases. We determined whether a lower lobe primary tumor location was associated with poor outcomes in the setting of stage I non-small-cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT).

Patients and methods: The data from consecutive patients with stage I NSCLC treated from 2009 to 2014 with curative intent SBRT were analyzed. Primary tumors in the right and left lower lobes were compared against the tumors in all other locations to determine whether a lower lobe location was associated with worse local, regional, and distant control and worse relapse-free and overall survival. The survival rates were estimated using Kaplan-Meier analysis, and multivariate analysis was completed using the Cox proportional hazards model, adjusting for age, stage, performance status, and radiation dose.

Results: A total of 122 patients with early-stage NSCLC who underwent SBRT were evaluated at a median follow-up period of 28.6 months. On multivariate analysis, lower lobe tumors were associated with poor relapse-free survival (hazard ratio [HR], 2.78; 95% confidence interval [CI], 1.21-7.76; P = .04) and poor overall survival (HR, 2.33; 95% CI, 1.09-5.64; P = .04). The 3-year relapse-free survival for patients with a lower lobe primary was 75% compared with 89% for patients with a non-lower lobe primary (P = .04). Additionally, the 3-year overall survival rate for patients with a lower lobe primary was 63% versus 82% in patients with a non-lower lobe primary (P = .01).

Conclusion: Lower lobe stage I NSCLC tumors treated with SBRT are associated with poor relapse-free and overall survival.

Keywords: Lung cancer; NSCLC; Prognostic factors; Radiation therapy; SBRT.