STIMULI investigated the efficacy and tolerability of the standard treatment (chemotherapy and radiotherapy) alone, compared with the standard treatment followed by nivolumab and ipilimumab (immunotherapy) in patients with limited stage SCLC. The results of STIMULI showed no significant difference between the immunotherapy and observation groups. Overall, there was no difference in the percentage of people with cancer progression at 12 and 24 months after starting immunotherapy or observation. There was also no difference in the percentage of people alive at 24 months, and the amount of tumour shrinkage was no different between the two groups. There was some data to suggest that immunotherapy after a more frequent radiotherapy schedule may be more effective, but this needs to be studied further.