Metastasis-Free Survival (MFS) is a clinical trial endpoint that measures the length of time from the start of treatment (or randomization) until the development of distant metastatic disease or death from any cause, whichever occurs first.
Definition
MFS = Time from treatment initiation to:
First occurrence of distant metastasis (confirmed radiologically or pathologically), or
Death from any cause
Context of Use
Commonly used in:
Prostate cancer (especially non-metastatic castration-resistant prostate cancer, nmCRPC)
Other solid tumors where distant spread is the key determinant of prognosis
Serves as a surrogate endpoint for overall survival in certain trials.
Advantages
Focuses on clinically meaningful progression (distant metastasis).
Can provide earlier readouts than overall survival (OS).
Useful in settings with long survival times but high risk of distant spread.
Limitations
May not capture local progression.
Imaging frequency and sensitivity may affect detection.
Not always validated as a true surrogate for OS in all cancers.