Sparing healthy lung by focusing the radiation beam flow onto the emphysematous regions in the treatment of lung cancer

Introduction: Currently, routine radiotherapy (RT) planning for locally advanced lung cancer (LC) does not take into consideration the functional state of the lung. The goal of this study was to determine if it is technically feasible to integrate the sites of pulmonary emphysema (PE) into the RT planning process.

Methods: Ten patients with LC and PE treated with helical Tomotherapy© were retrospectively included. After extraction by Myrian© software based on diagnostic CT (DCT), the PE data were transferred to the treatment planning system (TPS). PE-optimized plans were performed for patients with significant PE, where the dose was focused onto the PE. We compared the PE-optimized RT plans to the initial RT plans.

Results: The median dose to the planning target volume (PTV) was 52 Gy (range, 36-66) in fractions of 2-3 Gy. The median PE volume was 220 cm³ (range: 12-1394), and six patients were eligible for a PE-optimized RT plan. Considering the lung without PE, the V20 and V30 variations were not significant (P > 0.05), the V5 decreased from 50% to 44% after re-planning (P < 0.05). The mean PTV D98 was 50 Gy versus 48 Gy (P < 0.05).

Conclusion: Focusing the RT beam flow on the PE structure rather than the healthy lung appears feasible, and may be a promising technique to help preserve pulmonary function and minimize RT-related pulmonary toxicity.