This is a single arm, multi-centre, phase II open label study of nivolumab with stereotactic body radiotherapy (SBRT) for early stage non-small cell lung cancer.

SBRT will be delivered in either 3 or 5 fractions for peripheral disease or 8 fractions in central disease. A flat dose of 240 mg nivolumab infusion will begin after the final fraction of SBRT, within 24 hours and typically on the same day. Nivolumab will subsequently be given every 2 weeks at a flat dose of 240 mg for a further 13 cycles followed by Nivolumab 480mg Q4W for 7 cycles until 20 cycles in total are complete, unless any study drug discontinuation criteria are met. Treatment (20 cycles) will take a minimum of 1 year to complete but may exceed this timeframe if treatment delays are encountered.

(Patients who have enrolled on Nivolumab Q2W 240mg regimen for 26 cycles and are beyond cycle 14 will receive 26 cycles Q2W in total to complete treatment).

Assessment of toxicities will be performed at each clinic visit during treatment, at 30 days after the final nivolumab infusion and until 100 days after the final nivolumab infusion. Changes in spirometry values and PFTs will be assessed throughout the trial.

Relapse rates will be assessed with staging CT scans at 3, 6, 12, 18 and 24 months post SBRT.

An exploratory assessment will be made of the effect pre-treatment pulmonary function tests (PFTs) have on outcome measures.