Clinical trials are set up to look at specific outcomes. In some trials, researchers set out to look at progression-free survival (PFS), a measure of how long someone is on a treatment before their cancer starts to grow. They can also look at overall survival (OS), or how long someone lives after starting on a treatment.
Some researchers and advocates say it makes sense to use PFS as a substitute for OS because results come in sooner. They also argue that PFS matters to patients, even if it doesn’t affect their OS. Other researchers and advocates disagree. They point out that PFS doesn’t always predict OS, and using it could lead patients to think a treatment is more effective than it actually is.
Below you can learn more about how PFS and OS are used to measure treatment effectiveness, why this statistical controversy exists, and what questions to ask about PFS and OS when you are thinking about entering a clinical trial or starting a new treatment.
- Cancer Today: Measuring Treatment Effectiveness
- National Center for Biotechnology Information (NCBI): Progression-Free Survival: What Does it Mean for Psychological Well Being or Quality of Life?
- The Oncologist: Endpoints for Assessing Drug Activity in Clinical Trials
- Journal of Cancer: Relationship Between Progression-Free Survival and Overall Survival in Oncology Randomized Clinical Trials
- Annals of Oncology: Statistical Controversies in Clinical Trials
- HealthNewsReview.org How one bit of medical jargon fuels public confusion about cancer treatments (NEW)