Disease-Free Survival (DFS)

Definition of Disease-Free Survival and What it Means

Disease-free survival is a statistic that is often used to compare two different anti-cancer therapies.

Disease-free survival (DFS) is a number that tells the chances of staying free of a disease or cancer after a particular treatment. It is the percentage of individuals in the treatment group who are likely to be free of the signs and symptoms of a disease after a specified duration of time. Disease-free survival rates are an indication of how effective a particular treatment is.

  • Also called: Relapse-free survival, RFS

    When you see the term disease-free survival used you will see the disease in question, the treatment being tested, the period of time, and the percentage of study participants who were disease-free at the end of that time period. However, it doesn't necessarily mean they are cured, it only covers the time period given. The disease may recur after that time period.

    Examples of a Disease-Free Survival Statistic

    Please note this is not an actual current statistic but is given only to show an example.

    • 'The 2-year disease-free survival for stage IIA Hodgkin lymphoma is 80 percent when treated with a new combination of drugs.'

    This means that after this particular treatment, about 80 percent of those treated are likely to be free of disease at 2 years.

    Use of Disease-Free Survival Statistics in Medical Research

    The disease in question may be a form of cancer or it may be a chronic condition or acute illness.

    The term is used in many different research studies to measure the effectiveness of a treatment or procedure.

    Unlike some other survival terms used in medical research, this does not refer to surviving death. The survival in question is being free of the disease, which is an even more positive outcome than simply still being alive.

    Very often, two treatment strategies are compared on the basis of the disease-free survival that is achieved in similar groups of patients. Disease-free survival is often used with the term overall survival when cancer survival is described.

    If a treatment has better disease-free survival than the treatments they compared it to, the researchers may recommend considering it as a treatment option. If it is a drug that must be approved by the FDA or other regulators, this is evidence in favor of it being approved.

    The percentage of test subjects who are disease-free is good if it is higher - 80 percent is better than 20 percent, for example. A study may also look at different time periods, for example, one year, two years, five years, etc. The rates at the different time periods will tell about the long-term effectiveness of the treatment.

    What Doesn't Disease-Free Survival Tell You?

    This statistic looks at only a specific time period. The treatment being tested may be effective for that time period, but the disease may still come back later. It can also be that the subjects still had the condition, such as a cancer, but below detectable levels. While it may be an indication that the disease is cured, it is not proof that a cure has been achieved.

    Another aspect of anti-cancer therapies, in particular, that may not be reflected in disease-free survival rates is that of adverse events, toxicity and side effects—both short-term and long-term.

    A research drug being studied in clinical trials, for instance, may be very good at killing the cancer cells but also very prone to causing toxicities and serious adverse events. Toxicities may be so significant that they reduce survival early on, but then the people in the study who survive the treatment go on to have improved disease-free survival compared to the standard treatment. This is a special problem that arises in cancer research and new drug development.

    In such cases, a candidate drug may be appropriate for particular kinds of patients who tend to tolerate the toxicities, perhaps younger patients, while older patients and/or patients whose health is more frail may not be good candidates for such a therapy.

    A Word from Verywell

    People are not statistics, but statistics when used appropriately can be a powerful tool for you and your doctor to settle on the best course of action. The "right therapy" for an individual may or may not be one that is creating headlines because of results in the latest clinical trial. If you have any questions about what these survival statistics may mean for your condition, discuss them with your health care team.

    Source:

    NCI Dictionary of Cancer Terms, National Cancer Institute, Accessed 2/23/2016.

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