Survival Terms Used in Cancer

Have you ever read a scientific article on cancer treatment results? If you have, you must have encountered terms related to survival that left you a little bit confused. Doctors use many different survival terms to describe prognosis and treatment outcomes. Here are 6 terms commonly used to describe survival. You can explore each term for a deeper explanation with examples. Please note that the statistics given in examples are not current actual statistics.


Median Survival

cancer survivor with sign
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Median survival is the measure of how long individuals will live with a certain disease or treatment. The chance of living beyond the time denoted by the median survival is 50%. If median survival is three years, each person is as likely to live less than three years as living for more than three years.


Overall Survival (OS)

Overall survival is an indication of the proportion of people within a group who are expected to be alive after a specified time, such as 90% at five years. It takes into account death due to any cause—both related and unrelated to the type of cancer in question. In this case, they are reporting what percentage of the group was still alive at that mark and not reporting how much longer they would be expected to live.


Cause-Specific Survival (CSS)

Cause-specific survival is a term similar to overall survival. When reported for a kind of cancer, it measures the proportion of people who are expected to die due to that cancer at a specified time. Unlike overall survival, it excludes death due to causes unrelated to the cancer. For example, a 5-year cause-specific survival for a specific lymphoma type of 85% means that 15% of patients died of that lymphoma before the five-year mark.


Disease-Free Survival (DFS)

Disease-free survival measures the proportion of people among those treated for the type of cancer in question who will remain free of disease at a specified time after treatment. An example would be a 2-year disease-free survival of 80% for patients treated with a new drug combination. In this case, it isn't related to death but rather to still having the cancer or not.


Progression-Free Survival (PFS)

Progression-free survival measures the proportion of people among those treated for a cancer whose disease will remain stable (without signs of progression) at a specified time after treatment. For example, a progression-free survival rate of 80% at two years means that the cancer did not grow or spread in four out of five of the study participants at the two-year mark. It is often used in discussing treatments for low-grade lymphomas which are slow-growing but difficult to cure.


Event-Free Survival (EFS)

Event-free survival is a measure of the proportion of people who remain free of a particular complication of disease (called an event) after treatment that is designed to prevent or delay that particular complication. For example, a treatment might be designed to prevent bone pain. In this case, reported bone pain would be the event that they are measuring. A 50% event-free survival at one year for a treatment means that half of the participants reported no bone pain during the year after treatment.

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