Progression-free survival (PFS) is a surrogate endpoint defined as follows (by ChatGPT):
Essentially, PFS refers to the period of time during a clinical study or treatment regimen in which a patient’s disease does not worsen or progress. For example, in cancer research, it measures the time from the start of treatment until the cancer shows signs of growth, spread, or relapse.
Understanding PFS is vital because it helps doctors and researchers evaluate the effectiveness of a treatment in controlling the disease. A longer PFS suggests that the treatment is successfully slowing disease progression. This metric is particularly important in clinical trials when comparing different treatment approaches or medications.
A key question is: do patients care about PFS? The answer may be yes, because better PFS is most often (but not always) correlated with longer survival. However, do patients value PFS independently of OS? This may be the case if their quality of life is better (i.e., they have fewer symptoms) during the pre-progression phase. Or they may have less anxiety if they know their cancer has not progressed.
What does literature say?
an article from Raphael et al. (2019) conducted a systematic literature review of studies evaluating whether patients with advanced cancer understand and value PFS. In total, 17 studies met the inclusion criteria. Of these:
Ten studies specifically presented patients with the term progression free survival as attribute choice. In the words used to define the PFS attribute, 6 studies used the term survival. Five studies clarified that PFS may not translate into better overall survival, and five studies explained that improvements in PFS may not reflect how well the patient feels. No study clarified that a PFS event could represent progression or death, and no study defined for the patient what constituted progression. The studies evaluated here underrepresented racial and ethnic minorities (median percentage of white patients, 88%; range, 77%-96%). Values and preferences may vary across cultural backgrounds, as different preferences regarding cost-effectiveness outcomes were assigned in North American versus Asian studies, although only a few studies were evaluated.
As can be seen in the table below, there is significant heterogeneity in terms of how the PFS was presented to the cancer patients surveyed.
In some of the studies, PFS was the most important attribute. In others, quality of life factors were more important. However, overall, it is clear that more research is needed to fully understand how patients perceive the value of PFS.
