What Is Progression-Free Survival?
Progression-free survival (PFS) measures the length of time during and after treatment that a patient lives without their cancer growing, spreading, or otherwise getting measurably worse.
PFS is often used as a trial outcome measure because it can typically be assessed sooner than overall survival, since researchers don't need to wait for a study group's ultimate survival outcomes to draw conclusions about whether a treatment is controlling the cancer's growth.
A meaningful improvement in PFS in a trial suggests a treatment is helping keep cancer under control for longer, though PFS improvements don't always translate into an overall survival benefit, which is why both measures are often reported together in trial results.
PFS is commonly reported alongside overall response rate (the percentage of patients whose tumors measurably shrank) and disease control rate (the percentage whose disease didn't progress, including those with stable disease), giving a more complete picture of a treatment's effect than any single measure alone.
Frequently Asked Questions
Is a longer progression-free survival always better than a shorter one?
Generally yes, as a sign of disease control, though it should be considered alongside overall survival and side-effect data, not in isolation.
Why don't all trials just report overall survival instead of PFS?
Overall survival often takes much longer to fully assess, so PFS is used as an earlier and still clinically meaningful outcome measure.