New guidelines recommend the use of CT surveillance after a curative treatment for lung cancer as survivors have a 3-6% risk per person year of developing a second primary lung cancer. Our analysis of 107 patients with second primary lung cancer treated by stereotactic ablative radiotherapy showed a comparable 3 years overall survival (60%) and local control rate (89%) as for an initial lung cancer. Toxicity was uncommon, despite the fact that 73% of patients had undergone a prior (bi)lobectomy. Our findings indicate that CT surveillance is also appropriate in patients who may be unfit, or unwilling, to undergo surgery.