Cancer endpoints- Progression-free survival


Progression-free survival (PFS)

PFS is considered an important endpoint in cancer studies and compete with Overall survival as the primary endpoint, depending on the nature of the study.

Definition: PFS is defined as the time from randomization until objective tumor progression or death. The precise definition of tumor progression is important and should be carefully detailed in the protocol.

The FDA document "Guidance for Industry Clinical Trial Endpoints for the Approval of Cancer Drugs and Biologics" gives advice concerning this important endpoint; particularly how to define the time to event and censoring. It also discusses some advantages and disadvantages of PFS:

Regulatory evidence: Surrogate for accelerated approval or regular approval

Study design: • Randomiomized studies essential • Blinding preferred • Blinded review recommended

Advantages: • Smaller samplesize and shorter follow-up necessary compared with survival studies • Measurement of stable disease included • Not affected by crossover or subsequent therapies • Generally based on objective and quantitative assessment

Disadvantages: • Not statistically validated as surrogate for survival in all settings • Not precisely measured; subject to assessment bias particularly in open-label studies • Definitions vary among studies • Frequent radiological or other assessments • Involves balanced timing of assessments among treatment arms

Hans Fagertun can assist you in the discussion whether to use PFS or OS as the primary endpoint.