Understanding Statistics Used to Guide Prognosis and Evaluate TreatmentThis section has been reviewed and approved by the Cancer.Net Editorial Board, 7/11 Key Messages
When people are diagnosed with cancer, one of the first things they may want to know is their chance of survival and recovery. Understanding survival statistics becomes extremely important, yet it can also be confusing. Read below to learn more about how survival statistics can be used to estimate a patient’s prognosis and determine the treatment options. Estimating how long people live after a cancer diagnosis Survival statistics, usually given as rates, describe the percentage of people with a certain stage and/or type of cancer who will be alive a certain time after the cancer is detected. Survival rates can be given for any length of time. Cancer statistics are usually given as a five-year relative survival rate; this describes the percentage of people with cancer who will be alive five years after diagnosis, excluding those who die from other diseases. Example: The five-year relative survival rate for cervical cancer is 69%, which means that about 69% of women with cervical cancer will still be living five years after diagnosis. Survival statistics are usually calculated for specific cancer stages (the stage is an indication of the size of the tumor, and whether and how far the cancer has spread) as survival statistics can vary by stage. Example: The five-year relative survival rate for early-stage bladder cancer is 71%. If, however, the cancer is diagnosed at a later stage, the five-year relative survival rate is 5%. Survival statistics for all stages of a cancer combined are referred to as an overall rate, such as the overall five-year relative survival rate for all prostate cancers, which, regardless of stage, is 99%. Calculating how many people are cancer free or have cancer that is not growing or spreading Five-year relative survival rates include all people who are alive five years after a cancer diagnosis, including those who are in remission (temporary or permanent absence of disease) or still being treated. Disease-free survival (sometimes abbreviated as DFS) statistics and progression-free survival statistics (sometimes abbreviated as PFS) are more specific survival statistics that are often used when evaluating cancer treatments. Disease-free survival rates refer only to the percentage of people who experience a complete remission after finishing treatment. Progression-free survival rates describe the percentage of people who do not experience any new tumor growth or cancer spread during or after treatment, including those whose disease has either completely or partially responded to treatment, or those whose disease is stable (the cancer is still present but not growing or spreading). The concept of “cure” In medicine, a disease is considered cured when it’s been successfully treated and does not return. The concept of “cure” is difficult to apply to cancer because undetected cancer cells can sometimes remain in the body after treatment, causing the cancer to return later (referred to as a recurrence or relapse). Many cancers are considered “cured” when there is no cancer detected five years after diagnosis. However, recurrence after five years is still possible. Determining prognosis Among the first questions often asked when a person is diagnosed with cancer is whether the cancer can be treated successfully. This is called a prognosis—the likely course and outcome of the cancer and the chances of recovery. Doctors use survival statistics to make predictions about prognosis. Example: A man diagnosed with testicular cancer may be said to have a favorable prognosis, as the overall five-year relative survival rate for testicular cancer is 95%. Similar to survival statistics, prognosis also depends on the stage of the cancer at diagnosis—how early the cancer is detected and if or how far it has spread. Example: If detected early, the five-year relative survival rate for colorectal cancer is 90%. For advanced stage colorectal cancer that has spread to distant parts of the body, the five-year relative survival rate is about 12%. Points to remember
Evaluating treatment options Five-year relative survival rates are commonly used as a way to evaluate and compare different treatment options. Although someone who has survived five years after a cancer diagnosis is not necessarily “cured,” the five-year relative survival statistic is considered a good indication that the cancer is responding to treatment and that the treatment is successfully extending the life of the individual with cancer. Survival statistics help doctors determine which treatments provide the most benefit to people with cancer, and whether the benefits outweigh any risks (such as unpleasant side effects) associated with the treatment. Learn about making decisions about cancer treatment.Points to remember
More Information Understanding Statistics on Incidence, Prevalence, and Mortality Last Updated: January 26, 2012 |