Definition: Median Progression-Free Survival (PFS) is the time (in months) from the start of treatment (or diagnosis) until the disease worsens (progresses) or the patient dies from any cause, whichever occurs first — calculated across all patients in a study.

“Median” means that half of the patients had progression (or died) before this time point, and half remained progression-free beyond it.

Use in neuro-oncology: PFS is a key indicator of how long a treatment can delay tumor growth or clinical deterioration. In glioblastoma, typical median PFS after standard therapy is around 6–9 months.

Important: PFS does not necessarily reflect overall survival, and may be affected by:

• Imaging interpretation variability (especially with pseudoprogression)
• Treatment toxicity
• Follow-up interval frequency