A Feasibility Study of Functional Lung Volume Preservation during Stereotactic Body Radiotherapy Guided by Gallium-(68) Perfusion PET/CT

SIMPLE SUMMARY: Lung stereotactic body radiation therapy (SBRT) has become a real alternative treatment for inoperable stage I-II non-small cell lung cancer and lung oligometastases with a high local tumor control rate. However, SBRT remains associated with significant pulmonary toxicity. Perfusion positron emission tomography/computed tomography (PET/CT) with (68)Ga-macroaggregated albumin ((68)Ga-perfusion) is a very attractive imaging tool for functional lung avoidance during radiotherapy planning. This single-center prospective study shows the feasibility of significantly decreasing the doses delivered to the lung functional volumes in the lung SBRT using (68)Ga-perfusion PET/CT while still respecting target volume coverage and doses to other organs at risk. ABSTRACT: The aim of this study was to assess the feasibility of sparing functional lung areas by integration of pulmonary functional mapping guided by (68)Ga-perfusion PET/CT imaging in lung SBRT planification. Sixty patients that planned to receive SBRT for primary or secondary lung tumors were prospectively enrolled. Lung functional volumes were defined as the minimal volume containing 50% (FV50%), 70% (FV70%) and 90% (FV90%) of the total activity within the anatomical volume. All patients had a treatment planning carried out in 2 stages: an anatomical planning blinded to the PET results and then a functional planning respecting the standard constraints but also incorporating “lung functional volume” constraints. The mean lung dose (MLD) in functional volumes and the percentage of lung volumes receiving xGy (VxGy) within the lung functional volumes using both plans were calculated and compared. SBRT planning optimized to spare lung functional regions led to a significant reduction (p < 0.0001) of the MLD and V5 to V20 Gy in all functional volumes. Median relative difference of the MLD in the FV50%, FV70% and FV90% was −8.0% (−43.0 to 1.2%), −7.1% (−34.3 to 1.2%) and −5.7% (−22.3 to 4.4%), respectively. Median relative differences for VxGy ranged from −12.5% to −9.2% in the FV50%, −11.3% to −7.2% in the FV70% and −8.0% to −5.3% in the FV90%. This study shows the feasibility of significantly decreasing the doses delivered to the lung functional volumes using (68)Ga-perfusion PET/CT while still respecting target volume coverage and doses to other organs at risk.