How do you fractionate SBRT for NSCLC abutting the chest wall or in which the PTV encompasses part of the chest wall?  

To reduce the incidence of chest wall pain, we typically treat lesions abutting chest wall to 70 Gy in 10 fractions. However, if the lesion is small (<3 cm), 50 Gy in 4 fractions can also be considered if we can meet the chest wall dose volume constraints (30 Gy < 30 CC ideally- if not, 30 Gy ...