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The five-year survival rate is a type of survival rate for estimating the prognosis of a particular disease, normally calculated from the point of diagnosis. Lead time bias due to earlier diagnosis can affect interpretation of the five-year survival rate. There are absolute and relative survival rates; the latter are more useful and commonly used. ==Relative and absolute rates== Five-year ''relative'' survival rates are more commonly cited in cancer 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 ''absolute'' 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 would increase chances of survival compared to the general population. A more plausible explanation is that this pattern reflects a selection effect of PSA screening, as screening tests tend to be used less often by socially disadvantaged population groups, who, in general, also have higher mortality.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Five-year survival rate」の詳細全文を読む スポンサード リンク
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