First in Human Phase 1 Clinical Trial of Stereotactic Irradiation to Achieve Lung Volume Reduction (SILVR) in Severe Emphysema

Abstract

Purpose

Only a subset of patients with severe emphysema qualify for lung volume reduction surgery or endobronchial valves. We previously demonstrated that Stereotactic Ablative Radiotherapy (SABR) of lung tumors reduces lung volume in treated lobes by creating localized lung fibrosis. We aimed to determine the safety and, secondarily, explore the efficacy of Stereotactic Irradiation for Lung Volume Reduction (SILVR) over 18 months following intervention in patients with severe emphysema.

Methods and materials

We conducted a single-arm prospective clinical trial in eligible patients with severe emphysema treated with unilateral SABR (45 Gy in three fractions) to a target within the most emphysematous region. Primary outcome was safety i.e., incidence of grade≥3 adverse events. Secondary outcomes of efficacy were also explored.

Results

Eight subjects received the intervention. Median (range) baseline characteristics were age 73 years (63-78), FEV₁% 28.5% (19.0-42.0), DLCO% 40% (24.0-67.0), and BODE index 5.5 (5-9). The incidence of grade≥3 adverse events was 3/8 (37.5%). The relative Δtarget lobe volume was -23.1% (-1.6,-41.5) and -26.5% (-20.6,-40.8) at six and 18 months, respectively. Absolute ΔFEV₁% was greater in subjects with BODE index ≤5 vs. ≥6 (+12.0% vs. -2.0%). The mean baseline lung density (in Hounsfield units, reflecting the amount of preserved parenchyma) within the intermediate dose volume (V_60BED3) correlated with the absolute Δtarget lobe volume at 18 months.

Conclusions

Stereotactic Irradiation for Lung Volume Reduction appears to be safe, with a signal for efficacy as a novel therapeutic alternative for patients with severe emphysema. SILVR may be most safe/effective in patients with lower BODE index and/or less parenchymal destruction.