CANCER PATIENTS ARE LIKELY TO FIND ​​th​at making treatment decisions requires adding complex medical terms to their vocabulary. One of the terms patients may hear is progression-free survival​, an outcome often used in clinical trials to measure a treatment’s effectiveness.

Progression-free survival refers to the length of time patients in a clinical trial are on a cancer treatment and don’t see their cancer grow. Overall survival is another outcome that can be measured in a clinical trial. It refers to the length of time patients survive after being diagnosed with cancer or starting a cancer therapy. Cancer treatments were traditionally approved by the U.S. Food and Drug Administration (FDA) only if studies showed they improved overall survival. Over the past decade, the FDA has been approving drugs that studies have found improve progression-free survival.

What Does Progression-Free Survival Mean for You?​

These questions can help you make​ informed treatment decisions: 

  • What are the potential risks and benefits of this cancer therapy?
  • What clinical trials found a progression-free survival benefit?
  • Have any studies found an overall survival benefit?
  • Are there clinical trials now looking at overall survival?
  • What other therapies should I also consider?

One benefit of using progression-free survival to measure a drug’s effectiveness is that the researchers can get results more quickly, says Amulya A. Nageswara Rao, a pediatric oncologist at the Mayo Clinic in Rochester, Minnesota. It can be especially useful when studying a drug to treat a rare disease, where there are fewer patients to enroll in clinical trials, she adds.

Many studies continue to follow patients after progression-free survival results are reported. These studies have shown that a benefit in progression-free survival does not always predict a corresponding benefit in overall survival. For example, in 2008 the FDA used progression-free survival data in its decision to grant accelerated approval for the immunotherapy drug Avastin (bevacizumab) to treat metastatic HER2-negative breast cancer. Three years later, results from the study showed Avastin did not improve overall survival, leading the FDA to withdraw the approval. Avastin is still used to treat other types of cancer.

Rao says that progression-free survival data is only one factor patients need to consider when making treatment decisions. “Patients need to be able to take into account the severity and aggressiveness of the disease, all available options, and what their own priorities are for treatment outcomes, and then have a discus​sion [with their doctors] that involves progression-free survival and overall survival,” says Rao. For rare and advanced cancers, she says, a drug that shows a progression-free survival benefit may be the best option.