Epidemiology of cancer

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.Most common cancers in US males, by occurrencein US males, by mortalityin US females, by occurrencein US females, by mortality 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. 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. 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. Observational epidemiological studies that show associations between risk factors and specific cancers mostly serve to generate hypotheses about potential interventions that could reduce cancer incidence or morbidity. Randomized controlled trials then test whether hypotheses generated by epidemiological studies and laboratory research actually result in reduced cancer incidence and mortality. In many cases, findings from observational epidemiological studies are not confirmed by randomized controlled trials. The most significant risk factor is age. According to cancer researcher Robert A. Weinberg, 'If we lived long enough, sooner or later we all would get cancer.' Essentially all of the increase in cancer rates between prehistoric times and people who died in England between 1901 and 1905 is due to increased lifespans. Although the age-related increase in cancer risk is well-documented, the age-related patterns of cancer are complex. Some types of cancer, like testicular cancer, have early-life incidence peaks, for reasons unknown. Besides, the rate of age-related increase in cancer incidence varies between cancer types with, for instance, prostate cancer incidence accelerating much faster than brain cancer.. It has been proposed that the age distribution of cancer incidence can be viewed as the distribution of probability to accumulate the required number of driver events by the given age. Over a third of cancer deaths worldwide (and about 75-80% of cancers in the United States) are due to potentially modifiable risk factors. The leading modifiable risk factors worldwide are: