Secondary Endpoint
Additional outcome measures in a clinical trial that provide supporting evidence about the treatment's effects, safety, or quality-of-life impact.
In Detail
Secondary endpoints are additional outcome measures in a clinical trial that provide supplementary information about the treatment's effects beyond the primary endpoint. While the primary endpoint determines whether the trial succeeds, secondary endpoints offer a more complete picture of the treatment's benefits and risks. Common secondary endpoints include quality of life, duration of response, time to symptom improvement, biomarker changes, safety measures, and pharmacokinetic parameters. For example, a cancer trial with overall survival as its primary endpoint might include secondary endpoints such as tumor response rate, progression-free survival, and patient-reported quality of life. Secondary endpoints are pre-specified in the study protocol and analysis plan, but the trial is not statistically powered for them in the same way it is for the primary endpoint. This means that results on secondary endpoints should be interpreted with more caution, a positive finding on a secondary endpoint may be suggestive rather than conclusive. Statistical adjustments for multiple comparisons are often applied to reduce the risk of false-positive findings across multiple secondary endpoints. Despite these caveats, secondary endpoint data is valuable for clinical decision-making, label claims, and health economics assessments. The FDA may allow secondary endpoint data to support supplemental indications or label expansions. For patients, secondary endpoints often address outcomes that matter most in daily life, such as symptom relief, functional capacity, or reduced side effects, even when the primary endpoint is focused on a clinical measure like survival.
Frequently Asked Questions
What does "Secondary Endpoint" mean in clinical trials?
Additional outcome measures in a clinical trial that provide supporting evidence about the treatment's effects, safety, or quality-of-life impact.
Why is "secondary endpoint" important for patients?
Understanding secondary endpoint helps patients and caregivers navigate clinical trial participation with confidence. It is part of the broader clinical research process that ensures treatments are safe and effective before reaching patients.
Related Terms
Primary Endpoint
The main outcome measure that a clinical trial is designed to evaluate, the specific result that determines whether the treatment is considered effective.
Statistical Significance
A mathematical determination that the observed results of a clinical trial are unlikely to have occurred by chance, typically defined as a p-value less than 0.05.
Clinical Trial
A research study that tests a medical treatment, drug, device, or intervention in human volunteers to determine whether it is safe and effective.
this entity is one of the U.S. clinical trials and research registries concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the NIH ClinicalTrials.gov registry data behind every per-entity page on the site.
In the the NIH ClinicalTrials.gov registry data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.
Source: ClinicalTrials.gov, 2026.