A survival analysis using the Kaplan-Meier method shows median survival of 24 months for drug A versus 18 months for drug B, with the log-rank test p = 0.03. What does this result indicate?
- A The overall survival curves differ significantly; drug A is associated with longer survival time ✓
- B Drug A is superior; the difference in medians is statistically significant and clinically meaningful
- C Drug A reduces the hazard of death by exactly 25% compared to drug B
- D Exactly 50% of patients on both drugs will be alive at 24 months
Correct answer: A. The overall survival curves differ significantly; drug A is associated with longer survival time
Explanation
The log-rank test (p = 0.03 < 0.05) indicates a statistically significant difference between the two survival curves, suggesting drug A is associated with longer survival. Median survival is the time at which 50% of patients have experienced the event, but the log-rank test compares the entire survival experience, not just medians. The hazard ratio (not the median difference) quantifies the relative hazard; p < 0.05 does not imply clinical meaningfulness alone.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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