Functional Lung Avoidance Planning Guided by Lung Perfusion PET/CT Versus Anatomical Planning for Lung Stereotactic Body Radiotherapy

Stereotactic body radiotherapy (SBRT) has an increasing role in the treatment of both primary and secondary lung tumors. However, lung SBRT remains associated with significant radiation induced lung injury (RILI). Indeed, the reported incidence of symptomatic radiation induced lung injury (grade≥2) in the published literature is up to 20%. A current challenge of lung SBRT is therefore to better preserve lung function and to reduce pulmonary toxicity. During standard lung SBRT planning, dose constraints are defined on the anatomical lung volume. This planning considers the lung as functionally uniform and does not take into account the variability of regional lung function distribution. Functional lung avoidance is an emerging concept in lung radiotherapy (RT). The technique aims at personalizing RT treatment planning to individuals' lung functional distribution, by sparing functional pulmonary areas while prioritizing delivery of high doses to non-functional regions. 68Ga-MAA lung perfusion PET/CT is a novel imaging modality for regional lung function assessment. As compared with conventional lung scintigraphy, lung perfusion PET/CT is inherently a vastly superior technology for image acquisition (higher sensitivity and spatial resolution, greater access to respiratory gated acquisition). A more accurate lung functional mapping improves the possibility of functional lung avoidance planning for SBRT. The hypothesis is that functional lung avoidance planning guided by 68Ga-MAA perfusion PET/CT, while delivering an optimal dose to the tumor, will reduce the frequency of RILI in patients treated with lung SBRT.