===== Progression-Free Survival =====

**[[Progression]]-Free [[Survival]] (PFS)** is a clinical trial endpoint that measures the length of time during and after treatment that a patient lives with a disease (typically cancer) without it worsening.

==== Definition ====
PFS is defined as the time from the start of treatment (or randomization) until:
  * **Objective disease progression**, as determined by standardized criteria (e.g., RECIST), or
  * **Death from any cause**, whichever occurs first.

==== Key Features ====
  * Indicates the **period of disease control** under a given therapy.
  * Does **not require death** to be observed.
  * Commonly used in oncology trials as a **surrogate endpoint** for overall survival (OS), especially when OS is difficult to measure in a timely manner.
  * Higher PFS values may suggest **greater efficacy** of the therapeutic intervention.

==== Limitations ====
  * May not always correlate with overall survival.
  * Interpretation can be affected by **assessment intervals** and **imaging frequency**.
  * Subject to **investigator bias** if not blinded.

==== Related Terms ====
  * [[Overall Survival (OS)]]
  * [[Response Evaluation Criteria in Solid Tumors (RECIST)]]
  * [[Disease-Free Survival (DFS)]]