===== 📊 Median Progression-Free Survival (PFS) =====

**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