The value of progression-free survival to patients with advanced-stage cancer.

Progression-free survival (PFS) is frequently used as a primary end point in oncology clinical trials. Employing PFS instead of overall survival as the primary outcome has the advantage that trial completion can be quicker with fewer patients required, and it is cheaper. PFS is sensitive to cytostatic as well as cytotoxic mechanisms of therapeutic intervention and directly measures the effect of the investigational treatment. Despite these practical advantages, it is unclear whether or not extending PFS provides discernable clinical benefit. New treatments that increase PFS may not be of sufficient value to patients with advanced-stage cancer unless accompanied by tangible quantity or quality of life advantages. Any symptom relief that patients gain from treatment resulting in tumor shrinkage or stabilization must be balanced against the toxic effects that drug therapy itself creates. Consequently, improved assessment of new treatments using patient-reported outcomes alongside PFS is crucial to enable communication between clinicians and patients and optimal decision-making about therapeutic options.