Oncology Clinical Trials: Interpretation of Hazard Ratio and Median PFS

Try to interpret the following survival analysis results from an oncology clinical trial:

  • Hazard Ratio (HR) for PFS = 0.58 (95% Confidence Interval [CI]: 0.49–0.70)
  • Median Progression-Free Survival (PFS) = 16.4 months

These values describe the efficacy of a treatment in delaying disease progression compared to a control group.

1. Interpretation of the Hazard Ratio (HR) for PFS = 0.58

  • Definition: The hazard ratio (HR) quantifies the relative risk of disease progression or death between two groups (e.g., treatment vs. control).
  • HR = 0.58 means:
    • The treatment group has a 42% lower risk (1 - 0.58 = 0.42 or 42% reduction) of disease progression or death compared to the control group.
    • Patients receiving the treatment are progressing more slowly than those in the control group.
  • 95% Confidence Interval (0.49–0.70):
    • The true hazard ratio is likely between 0.49 and 0.70 in 95% of similar trials.
    • Since the entire CI is below 1, the result is statistically significant (indicating a real treatment benefit).
    • If the CI had crossed 1.0, the result would be not statistically significant.

2. Interpretation of Median PFS = 16.4 Months

  • Definition: Median PFS is the time at which 50% of patients in the treatment group have experienced disease progression or death.
  • Interpretation:
    • This means that half of the patients remained progression-free for at least 16.4 months, while the other half progressed before that.
    • Comparison with Control Group: If the control group had a median PFS of, say, 9 months, this suggests that the treatment prolongs disease control significantly.

3. Combined Interpretation

  • The hazard ratio (0.58) tells us that the risk of progression is reduced by 42% in the treatment group.
  • The median PFS (16.4 months) tells us that patients remain progression-free for a median of 16.4 months.
  • If the control group's median PFS is much shorter (e.g., 9 months), this reinforces the benefit of the treatment.
  • The statistically significant 95% CI (0.49–0.70) strengthens the confidence in the result.

Conclusion

This data suggests that the treatment significantly delays disease progression, as shown by the 42% risk reduction (HR = 0.58) and longer median PFS (16.4 months). If supported by overall survival (OS) benefits and good safety data, this would indicate a strong therapeutic advantage.

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