The five-year survival rate

Survival rate

In biostatistics, survival rate is a part of survival analysis, indicating the percentage of people in a study or treatment group who are alive for a given period of time after diagnosis...

is a term used in medicine for estimating the prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

 of a particular disease.

Analysis performed against the Surveillance, Epidemiology, and End Results database

Surveillance, Epidemiology, and End Results database

The Surveillance, Epidemiology, and End Results database is a resource which allows statistical analysis to be performed upon data collected by cancer registries.It is maintained by the National Cancer Institute....

 (SEER) facilitates calculation of Five-year survival rates.

Lead time bias

Lead time bias

Lead time is the length of time between the detection of a disease and its usual clinical presentation and diagnosis ....

 due to earlier diagnosis can affect interpretation of the five-year survival rate.

Relative and absolute rates

Five-year relative survival

Relative survival

When describing the survival experience of a group of people or patients typically the method of overall survival is used, and it presents estimates of the proportion of people or patients alive at a certain point in time...

 rates are more commonly cited in cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 statistics; five-year absolute survival rates may sometimes also be cited.

• Five-year absolute survival rates describe the percentage of patients that are alive five years after their disease is diagnosed.

• Five-year relative survival rates describe the percentage of patients with a disease that are alive five years after their disease is diagnosed divided by the percentage of the general population of corresponding sex and age that are alive after five years. Typically, cancer five-year relative survival rates are well below 100%, reflecting excess mortality among cancer patients compared to the general population. In contrast to five-year absolute survival rates, five-year relative survival rates may also equal or even exceed 100% if cancer patients have the same or even higher survival rates than the general population. This pattern may occur if cancer patients can generally be cured, or if patients diagnosed with cancer are otherwise more privileged (e.g., in terms of socioeconomic factors or access to medical care) than the general population.

The fact that relative survival rates above 100% were estimated for some groups of patients appears counter-intuitive on first view. It is unlikely that occurrence of prostate cancer

Prostate cancer

Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

 would increase chances of survival compared to the general population. A more plausible explanation is that this pattern reflects a selection effect

Selection bias

Selection bias is a statistical bias in which there is an error in choosing the individuals or groups to take part in a scientific study. It is sometimes referred to as the selection effect. The term "selection bias" most often refers to the distortion of a statistical analysis, resulting from the...

 of PSA screening, as screening

Screening (medicine)

Screening, in medicine, is a strategy used in a population to detect a disease in individuals without signs or symptoms of that disease. Unlike what generally happens in medicine, screening tests are performed on persons without any clinical sign of disease....

 tests tend to be used less often by socially disadvantaged population groups, who, in general, also have higher mortality.

Uses

Five-year survival rates can be used to compare the effectiveness of treatments.

Use of 5-year survival statistics is more useful in aggressive diseases that have a shorter life expectancy following diagnosis (such as lung cancer

Lung cancer

Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

) and less useful in cases with a long life expectancy such as prostate cancer

Prostate cancer

Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

.

Improvements in rates are sometimes attributed to improvements in diagnosis, rather than improvements in prognosis.

To compare treatments (independent of diagnostics) it is better to consider survival from reaching a certain stage of the disease.