Understanding Statistics Used to Guide Prognosis and Evaluate Treatment

Approved by the Cancer.Net Editorial Board, 08/2018

One of the first questions people diagnosed with cancer may ask is, “what’s the chance of survival?”

Doctors use statistics to provide an answer. Statistics are estimates that describe trends in large numbers of people. They can help with predictions. But they cannot tell what will actually happen to a person.

Survival statistics vary based on these factors:

  • Type of cancer

  • The stage of cancer

  • Age

  • Time period

Ask your health care team for the most appropriate statistics for your situation. And ask them to explain the statistics that seem unclear.

Survival statistics

Doctors use survival statistics to estimate a patient’s prognosis. Prognosis is the chance of recovery. Survival statistics also help doctors evaluate treatment options.

Researchers usually give survival statistics as rates for specific cancer types.

Survival rate. The percentage of people who will be alive at a certain time after diagnosis.

Survival rates can describe any given length of time. However, researchers usually give cancer statistics as a 5-year relative survival rate.

5-year relative survival rate. The percentage of people who will be alive 5 years after diagnosis. It does not include those who die from other diseases.

Sometimes, this includes all people with a specific cancer type. Researchers call this an overall rate.

Example: The 5-year relative survival rate for women with cervical cancer is about 67%. This means that about 67 out of every 100 women with cervical cancer will be alive 5 years after diagnosis.

Researchers also calculate survival statistics for specific cancer stages. The stage helps describe where a cancer is located, if or where it has spread, and whether it is affecting other parts of the body. Survival statistics can vary by stage.

Example: The 5-year relative survival rate for early-stage cervical cancer is 92%. This means that 92 out of every 100 women with early-stage cervical cancer will be alive 5 years after diagnosis.

Researchers base 5-year survival statistics on people whose cancer was treated at least 5 years ago. The statistics may not reflect the latest treatment advances.

Disease-free and progression-free survival rates

Five-year relative survival rates include people in remission. Remission is the temporary or permanent absence of disease. This survival rate also includes those still receiving treatment

Disease-free survival (DFS) statistics and progression-free survival (PFS) statistics are more specific. Doctors often use them to evaluate cancer treatments.

Disease-free survival rate. The percentage of people in complete remission after finishing treatment.

Progression-free survival rate. The percentage of people who did not have new tumor growth or cancer spread during or after treatment. The disease may have responded to treatment completely or partially. Or the disease may be stable. This means the cancer is still there but not growing or spreading.

Using survival statistics to determine prognosis

A favorable prognosis means a good chance of treatment success. For example, the overall 5-year relative survival rate for testicular cancer is 95%. This means that most men diagnosed with the disease have a favorable prognosis.

Prognosis depends on the stage of the cancer at diagnosis. For example, the 5-year relative survival rate for early-stage colorectal cancer is 90%. For advanced-stage colorectal cancer, the rate drops to about 14%.

Using survival statistics to evaluate treatment options

Doctors often use 5-year relative survival rates to evaluate and compare treatment options. They consider the survival rate a good indication of the following:

  • Whether the cancer will respond to treatment

  • Whether the treatment will successfully extend the person’s life

Survival statistics help doctors decide which treatments provide the most benefit. And they help doctors weigh the benefits against the risks. For example, a specific treatment may very effective in treating the cancer but a person might experience unpleasant side effects from it.

Statistics can provide helpful information but they are not the only factor used for treatment planning. Learn more about making decisions about cancer treatment.

The concept of “cure”

The word "cure" does not apply perfectly to cancer. Sometimes undetected cancer cells are still in the body after treatment. These cells can cause the cancer to come back later. Doctors call this a recurrence or relapse.

The medical community considers many cancers “cured” when doctors cannot detect cancer 5 years after diagnosis. But recurrence after 5 years is still possible.

Statistics adapted from the American Cancer Society's publication, Cancer Facts & Figures 2018.

Related Resources

Understanding Statistics Used to Estimate Risk and Recommend Screening

Understanding Cancer Risk

What is Survivorship?

More Information

National Cancer Institute Surveillance Epidemiology and End Results (SEER) Program