Hazard Ratio — What It Means in Clinical Trials
Plain English Definition
A hazard ratio (HR) compares the rate of an event (like death or disease progression) between two groups. A hazard ratio of 1.0 means no difference. Below 1.0 means the treatment group did better. Above 1.0 means the treatment group did worse. For example, an HR of 0.70 means the treatment group had a 30% lower rate of the event.
Why It Matters
Hazard ratios are the most common way to report survival results in cancer trials. An HR below 1.0 is what you want to see — it means the new treatment reduces the risk compared to the control.
Example
A trial might report: "Hazard ratio for overall survival: 0.75 (p=0.01)." This means the treatment reduced the risk of death by 25% compared to the control.
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