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The epidemiology of cancer is the study of the factors affecting cancer, as a way to infer possible trends and causes. The study of cancer epidemiology uses epidemiological methods to find the cause of cancer and to identify and develop improved treatments. This area of study must contend with problems of lead time bias and length time bias. Lead time bias is the concept that early diagnosis may artificially inflate the survival statistics of a cancer, without really improving the natural history of the disease. Length bias is the concept that slower growing, more indolent tumors are more likely to be diagnosed by screening tests, but improvements in diagnosing more cases of indolent cancer may not translate into better patient outcomes after the implementation of screening programs. A related concern is overdiagnosis, the tendency of screening tests to diagnose diseases that may not actually impact the patient's longevity. This problem especially applies to prostate cancer and PSA screening. Some cancer researchers have argued that negative cancer clinical trials lack sufficient statistical power to discover a benefit to treatment. This may be due to fewer patients enrolled in the study than originally planned. == Organizations == State and regional cancer registries are organizations that abstract clinical data about cancer from patient medical records. These institutions provide information to state and national public health groups to help track trends in cancer diagnosis and treatment. One of the largest and most important cancer registries is Surveillance Epidemiology and End Results (SEER), administered by the US Federal government.〔(【引用サイトリンク】title=SEER Surveillance Epidemiology and End Results )〕 Health information privacy concerns have led to the restricted use of cancer registry data in the United States Department of Veterans Affairs and other institutions. The American Cancer Society predicts that approximately 1,690,000 new cancer cases will be diagnosed and 577,000 Americans will ultimately die of cancer in 2012.〔(【引用サイトリンク】Cancer Facts and Figures 2012 )〕 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「Epidemiology of cancer」の詳細全文を読む スポンサード リンク
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