This study uses durvalumab (MEDI 4736), an experimental type of drug made by Astra Zeneca Pharmaceuticals, (limited partnership) LP, which in early studies has shown to possibly reduce the growth of certain types of lung cancer. The Investigators will enroll up to 105 subjects into the study. After an initial safety sample of 15 individuals receiving durvalumab (MEDI 4736) and Stereotactic Ablative Body Radiotherapy (SABR), if it is shown to be safe to administer this combination of therapies, the next enrolled subjects will be randomized in a 1:1 fashion (each subject with a "50-50 chance" like the flip of a coin) to receive either SABR and durvalumab (MEDI 4736), or SABR alone.