(OA03) A Phase II Study of Stereotactic Body Radiotherapy and Stereotactic Body Proton Therapy for High-Risk Medically Inoperable Early-Stage Non-Small Cell Lung Cancer

Abstract

We sought to compare the toxicity and efficacy of stereotactic body radiotherapy (SBRT) versus stereotactic body proton therapy (SBPT) for high-risk medically inoperable early-stage non-small cell lung cancer (NSCLC). We randomly assigned patients with medically inoperable NSCLC with high-risk features (centrally located or <5 cm-T3 tumor or isolated lung parenchymal recurrences) to SBRT or SBPT. Radiation dose was 50 Gy(RBE) in four 12.5-Gy(RBE) fractions prescribed to the planning target volume. SBRT was given as 3-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT), and SBPT was given as passive scattering. Consistency in patient setup was ensured with on-board cone-beam computed tomography for the SBRT group and with orthogonal X-rays for the SBPT group. The study closed early owing to poor accrual, largely because of patient preference, insurance coverage, and lack of volumetric imaging in SBPT group. Ultimately, 21 patients were enrolled, and 19 patients who received 50 Gy in 4 fractions were included for analysis (9 SBRT, 10 SBPT). At a median follow-up time of 32 months, median overall survival (OS) time was 28 months in the SBRT group and not reached in the SBPT group. Three-years OS were 27.8% and 90%, 3-year local control (LC) were 87.5% (8/9) and 90.0% (9/10) and 3-years regional control (RC) were 47.6% (5/9) and 90% (9/10) in SBRT and SBPT respectively. One patient in the SBPT group developed grade 3 skin fibrosis. No patients experienced grade 4/5 toxicity. This is the first randomized phase II study to compare SBRT with SBPT for high-risk medically inoperable early-stage NSCLC. Although poor accrual led to early closure of the trial and precluded assessment of efficacy, both techniques seemed to have acceptable toxicity, and outcomes after SBPT were no worse than those after SBRT.