What is this summary about?This plain language summary reports the results of the IPSOS clinical study. This study looked at treatment with atezolizumab (a type of immunotherapy) compared with single-agent chemotherapy (1 chemotherapy drug; either vinorelbine or gemcitabine) in participants receiving their first treatment for advanced or metastatic non-small cell lung cancer (NSCLC).People with advanced or metastatic NSCLC are often treated with platinum-based chemotherapy, which is a combination of 2 drugs. However, a doctor may decide that some people are not suitable candidates for platinum-based chemotherapy because they are too weak, or they are older and have other medical conditions. These people who should not receive platinum-based chemotherapy are often treated with 1 chemotherapy drug (single-agent chemotherapy) instead.People who are weaker, older, or have other medical problems are often not allowed to participate in clinical trials for new medicines. Therefore, these patients are not well represented in clinical trials. The IPSOS study focused on these under-represented patients.The IPSOS study compared how well atezolizumab worked compared with single-agent chemotherapy (vinorelbine or gemcitabine) in participants who should not receive platinum-based chemotherapy.Researchers collected information about the health of participants for an average of more than 3 years after starting treatment.What were the results?Compared with single-agent chemotherapy, atezolizumab improved how long participants lived after starting treatment. After 2 years, the percentage of participants still alive was twice as high in the atezolizumab group (24%) compared with the chemotherapy group (12%), despite over 50% of patients in the chemotherapy group who were still alive at 2 years receiving subsequent immunotherapy. Throughout their treatment, participants in the atezolizumab group reported no change in their health and ability to function and enjoy life, while participants in the chemotherapy group reported worsening in some of these measures. Compared with single-agent chemotherapy, atezolizumab was associated with a similar rate of serious side effects (those that were life-threatening, needed hospital care, or caused lasting problems or death) related to treatment and half the rate of severe side effects (those considered medically important by a person’s doctor; also called ‘Grade 3, 4, or 5’) related to treatment.What do the results of the study mean?Atezolizumab is now approved by the European Medicines Agency and can be used as a first treatment for people with advanced or metastatic NSCLC who aren’t able to receive platinum-based chemotherapy.[Box: see text]. eng