Definition of Survival Rate for Cancer

What Does Cancer Survival Rate Mean?

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What is meant by the term survival rate?. istockphoto.com

Definition: Survival Rate

Survival rate is defined as the percent of people who survive a disease such as cancer for a specified amount of time. For example, if the 5-year survival rate for a particular cancer is 34 percent, this means that 34 out of 100 people initially diagnosed with that cancer would be alive after 5 years. Survival rate does not indicate if a cancer is cured or if treatment is completed.

Median Survival

Another term that is often used when talking about survival rates is median survival. Median survival time is the amount of time after which 50 percent of people have died, and 50 percent are still alive.  Many clinical studies report median survival rather than survival rate, especially in advanced cancers.

Overall Survival (OS)

Overall survival (OS) is another term often used in reference to treatments for cancer.  It refers to the time which begins at diagnosis (or at the start of treatment) and up to the time of death.  It is usually used as an indication of how well a treatment works.

Progression-Free Survival (PFS)

Progression-free survival (PFS) is a term often used in clinical trials evaluating new drugs and treatments.  It refers to the amount of time between when a treatment for cancer begins, and when the cancer progresses or death occurs. 

Disease-Free Survival

Disease-free survival is a measure of the number of people who are expected to be free from cancer for a particular amount of time.

This is also sometimes referred to as "relapse-free survival." Note that overall survival includes both those who are surviving without any evidence of cancer and those who are surviving but still have cancer present in their boy.

Cause-Specific Survival

Cause-specific survival is an important term in clinical studies and refers to the number of people surviving a particular cancer after a period of time.

An example is the easiest way to describe this. Whereas overall survival from lung cancer includes not only those people who die from lung cancer, but also heart disease, other cancers, and any other condition, cause-specific survival refers to only the likelihood that someone would survive lung cancer alone. This is important in evaluating potential treatments. A theoretical strong drug which damages the heart may increase cause-specific survival from lung cancer but could actually lower overall survival rates due to deaths from heart disease.

Event-Free Survival

Event-free survival refers to the percent of people who survive without a particular complication over a period of time. For example, this term could represent the number of people who did not develop neurological symptoms or bone pain due the spread of a lung cancer to the brain or the bones.

Lung Cancer Survival Rates by Type and Stage:

This article lists survival based on different types and stages of lung cancer.  Note that even within the same type and stage, cancers are all different and all have different molecular profiles.

These are further broken down into:

Comment About Survival Rate Statistics

Keep in mind that survival rates are based on statistics and look at the population as a whole. Your prognosis may be different based on many variables such as your general health, and new treatments that have become available. By the time survival rates are published, the statistics are frequently several years old.  For example, when reporting the average 5-year survival rate for a type and stage of cancer, statistics are looking at people who were diagnosed at least 5 years before the study results were reported.  With advances in the treatment of even advanced cancers, these numbers may not take into account changes in current treatment recommendations, and your own expected survival rate could be considerably higher.

With regard to lung cancer, it is even more important to consider that survival rates may not reflect your outcome from the disease.  There have been many recent advances in treatment, and an example may help explain this much better.  Between 2011 and 2015 there were more new treatments approved for lung cancer - even advanced lung cancer - than had been approved in the 40 year period prior to 2011.  In 2016, there are more new drugs being tested in clinical trials for lung cancer than for any other type of cancer.  If you've been recently diagnosed with lung cancer, keep in mind that there are many reasons to feel hope.

Further Reading:

Sources:

American Cancer Society. Non-Small Cell Lung Cancer Survival Rates by Stage. Updated 05/16/16. http://www.cancer.org/cancer/lungcancer-non-smallcell/detailedguide/non-small-cell-lung-cancer-survival-rates

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