Progression-free survival is an endpoint used in cancer studies. It measures how much time passes (usually measured in months) from when someone with cancer receives treatment until the person’s cancer begins growing again.
Deeper dive
A common endpoint in cancer trials in particular is survival, but it’s important to note whether a study is referring to overall survival or progression-free survival. Overall survival is just what it sounds like — how long a person survives at all, regardless of their condition, the progression of their disease or their quality of life. Progression-free survival (often abbreviated PFS) starts at the point when a person begins receiving the treatment being studied and then refers to how much time passes with the person’s disease not worsening. With cancer, that means the time that passes without a tumor growing or the cancer spreading, even if it doesn’t shrink. Progression-free survival can be used with other conditions as well, however, such as arthritis and various rheumatic and other autoimmune conditions. Similarly, in those cases, it refers to how long a person goes without their symptoms getting any worse.
Sometimes progression-free survival is used as a surrogate endpoint for overall survival, as seen in this study about chronic lymphocytic leukemia. As noted in the background information, “The endpoints of progression-free survival and time-to-progression are frequently used to evaluate the clinical benefit of anticancer drugs.” Since “the surrogacy of those endpoints for overall survival is not validated in all cancer settings,” this study involved a systematic review of the research to analyze whether progression-free survival could stand in adequately enough for overall survival to become a surrogate endpoint.
Finally, keep in mind that lead time bias can artificially inflate the length of a person’s survival and lead to incorrect assumptions about the benefit of a treatment.