Correct interpretation of clinical trial results is important. Overall survival was once considered the primary endpoint for neoplastic disease, but surrogate endpoints are increasingly being used for diseases whose prognosis has improved. This is due to the longer trial duration required to obtain conclusions and to poor statistical power. Clinical decision-making in practice is also shifting to using these surrogate endpoints. In clinical trials, eligibility criteria are set to obtain differences between arms. However, this does not mean that results should only be applied to eligible populations, as it is not realistic to conduct a clinical trial in patients with all possible characteristics. Rather, results should be applied to patients who do not meet the eligibility criteria, with careful consideration. A single clinical trial often presents the results of many subgroup analyses, but the main conclusion should not be judged differently by subgroup. The purpose of subgroup analysis is to find potential confounders that interact with the conclusion, and results of subgroup analysis should not be overestimated. Non-inferiority trials have become increasingly common in recent years, and their importance is not limited to demonstrating the non-inferiority of the primary endpoint. Specifically, they are also important for understanding the benefits in the experimental arm outside those in primary analysis. Some secondary endpoints are very important for making conclusions about these benefits.
Keywords: Eligibility criteria; Non-inferiority trial; Primary endpoint; Subgroup analysis.