Biologically Effective Dose in Stereotactic Body Radiotherapy and Survival for Patients With Early-Stage NSCLC

Abstract

Introduction: Stereotactic body radiotherapy (SBRT) results in excellent local control of stage I NSCLC. Radiobiology models predict greater tumor response when higher biologically effective doses (BED₁₀) are given. Prior studies support a BED₁₀ greater than or equal to 100 Gy with SBRT; however, data are limited comparing outcomes after various SBRT regimens. We therefore sought to evaluate national trends and the effect of using "low" versus "high" BED₁₀ SBRT courses on overall survival (OS).

Methods: This retrospective study used the National Cancer Data Base to identify patients diagnosed with clinical stage I (cT1-2aN0M0) NSCLC from 2004 to 2014 treated with SBRT. Patients were categorized into LowBED (100-129 Gy) or HighBED (≥130 Gy) groups. A 1:1 matched analysis based on patient and tumor characteristics was used to compare OS by BED₁₀ group. Tumor centrality was not assessed.

Results: O 25,039 patients treated with LowBED (n = 14,756; 59%) or HighBED (n = 10,283; 41%) SBRT, 20,542 were matched. Shifts in HighBED to LowBED SBRT regimen use correlated with key publications in the literature. In the matched cohort, 5-year OS rates were 26% for LowBED and 34% for HighBED groups (p = 0.039). On multivariate analysis, receipt of LowBED was associated with significantly worse survival (hazard ratio = 1.046, 95% confidence interval: 1.004-1.090, p = 0.032).

Conclusions: LowBED SBRT for treating stage I NSCLC is becoming more common. However, our findings suggest SBRT regimens with BED₁₀ greater than or equal to 130 Gy may confer an additional survival benefit. Additional studies are required to evaluate the dose-response relationship and toxicities associated with modern HighBED SBRT.

Keywords: Biologically effective dose; Early-stage lung cancer; NSCLC; Stereotactic ablative radiation therapy; Stereotactic body radiation therapy.