Target Volume Delineation in Non-small Cell Lung Cancer
Radiation therapy (RT) is an established treatment for all stages of non-small cell lung cancer (NSCLC), from definitive RT for early-stage disease to palliative RT for advanced and metastatic disease. Identifying the appropriate RT target for each patient starts at the time of consultation, where the radiation oncologist synthesizes the patient’s history, physical exam, imaging, and pathology with evidence-based treatment paradigms. When RT is recommended, the treatment planning workflow starts with a three-dimensional (and now often a four-dimensional) computed tomography (CT) simulation, which has largely supplanted two-dimensional treatment planning. Following CT simulation, the radiation oncologist delineates target volumes and organs at risk, defines planning objectives, and then engages in an iterative process of plan optimization and plan evaluation, culminating in image-guided radiation therapy (IGRT). These steps are intertwined; for instance, the reproducibility of patient setup and the type of image guidance used are reflected in the target volume margins. The steps may also vary based on the treatment intent and technique, with different workflows for stereotactic body radiation therapy (SBRT) for early-stage (or oligometastatic) disease, three-dimensional conformal radiation therapy (3D CRT) or intensity-modulated radiation therapy (IMRT) for locoregionally advanced disease, and palliative RT for symptomatic metastatic disease.
