Cancer screening
Encyclopedia
Cancer screening aims to detect cancer
before symptoms appear. This may involve blood tests
, urine tests, other tests, or medical imaging
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
and false negative results
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through lead time bias
or length time bias
.
Cancer screening aims to detect cancer
before symptoms appear. This may involve blood tests
, urine tests, other tests, or medical imaging
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
and false negative results
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through lead time bias
or length time bias
.
Cancer screening aims to detect cancer
before symptoms appear. This may involve blood tests
, urine tests, other tests, or medical imaging
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
and false negative results
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through lead time bias
or length time bias
.
There is some controversy however about the number of lives saved by breast screening and the number of cancers diagnosed and treated that would not have caused any health problems in the participants' lifetime, sometimes known as over-diagnosis and over-treatment.
Non-invasive breast cancers, or Ductal Carcinoma in Situ, sometimes progress to invasive cancer but sometimes do not. Since doctors cannot usually distinguish which DCIS will go on to invasive cancer, most are treated. This is where over-treatment can arise.
The U.S. Preventive Services Task Force
(USPSTF) recommends populationscreening mammography once for every two years for all women aged 50—74, with decisions about screening younger and older women being determined by consideration of the individual's risk factors and the benefits and harms of screening. They do not recommend either breast self-examination
or clinical breast examination. Their recommendation is similar to the World Health Organization
's, and less aggressive than most North American organizations.
The U.S. Preventive Services Task Force
(USPSTF) strongly recommends cervical cancer
screening in American women who are sexually active and have a cervix
at least until the age of 65, usually every three years. Their recommendation is typical of professional organizations and other government agencies in the US and Canada.
The US Preventive Services Task Force recommends screening for bowel cancer using fecal occult blood testing, sigmoidoscopy, or colonoscopy, in adults, beginning at age 50 years and continuing until age 75 years.
, the PSA
test may detect small cancers that would never become life threatening, but once detected will lead to treatment. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. Follow up procedures used to diagnose prostate cancer (prostate biopsy
) may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence
(inability to control urine flow) and erectile dysfunction
(erections inadequate for intercourse).
(USPSTF), there is insufficient evidence to recommend for or against screening for lung cancer
.
Recent research suggests that screening heavy smokers may be effective.
There is insufficient evidence to recommend for or against screening for skin cancer
, and oral cancer
. Routine screening is not recommended for bladder cancer
, testicular cancer
, ovarian cancer
, and pancreatic cancer
.
According to the U.S. Preventive Services Task Force
(USPSTF), there is insufficient evidence to recommend for or against screening for prostate cancer in men under 75. Routine screening is not recommended for prostate cancer in men over 75. Most North American medical groups recommend individualized decisions about screening, taking into consideration the risks, benefits, and the patients' personal preferences.
to search for cancer in people without clear symptoms is similarly marred with problems. There is a significant risk of detection of what has been recently called an incidentaloma
- a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations.
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...
before symptoms appear. This may involve blood tests
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
, urine tests, other tests, or medical imaging
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
and false negative results
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through 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 ....
or length time bias
Length time bias
Length time bias is a form of selection bias, a statistical distortion of results which can lead to incorrect conclusions about the data. Length time bias can occur when the lengths of intervals are analysed by selecting intervals that occupy randomly chosen points in time or space...
.
Making screening decisions
The following criteria are used by the UK National Screening Committee for making decisions about whether to introduce a screening test for a population.Cancer screening aims to detect 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...
before symptoms appear. This may involve blood tests
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
, urine tests, other tests, or medical imaging
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
and false negative results
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through 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 ....
or length time bias
Length time bias
Length time bias is a form of selection bias, a statistical distortion of results which can lead to incorrect conclusions about the data. Length time bias can occur when the lengths of intervals are analysed by selecting intervals that occupy randomly chosen points in time or space...
.
Making screening decisions
The following criteria are used by the UK National Screening Committee for making decisions about whether to introduce a screening test for a population.Cancer screening aims to detect 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...
before symptoms appear. This may involve blood tests
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
, urine tests, other tests, or medical imaging
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.
Universal screening, mass screening or population screening involves screening everyone, usually within a specific age group. Selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening can lead to false positive results and subsequent invasive procedures. Screening can also lead to false negative results, where an existing cancer is missed. Controversy arises when it is not clear if the benefits of screening outweigh the risks of the screening procedure itself, and any follow-up diagnostic tests and treatments.
Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
and false negative results
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...
. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. Early diagnosis may lead to higher rates of successful treatment and extended life. However, it may also falsely appear to increase the time to death through 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 ....
or length time bias
Length time bias
Length time bias is a form of selection bias, a statistical distortion of results which can lead to incorrect conclusions about the data. Length time bias can occur when the lengths of intervals are analysed by selecting intervals that occupy randomly chosen points in time or space...
.
Making screening decisions
The following criteria are used by the UK National Screening Committee for making decisions about whether to introduce a screening test for a population. http://www.scotland.gov.uk/Topics/Health/health/cancer/Cancer-Screening/criteriaThe Condition
- The condition should be an important health problem
- The epidemiology and natural history of the condition, including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage
- All the cost-effective primary prevention interventions should have been implemented as far as practicable
- If the carriers of a mutation are identified as a result of screening the natural history of people with this status should be understood, including the psychological implications
The Test
- There should be a simple, safe, precise and validated screening test
- The distribution of test values in the target population should be known and a suitable cut-off level defined and agreed
- The test should be acceptable to the population
- There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result and on the choices available to those individuals
- If the test is for mutations the criteria used to select the subset of mutations to be covered by screening, if all possible mutations are not being tested, should be clearly set out
The Treatment
- There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment
- There should be agreed evidence based policies covering which individuals should be offered treatment and the appropriate treatment to be offered
- Clinical management of the condition and patient outcomes should be optimised in all health care providers prior to participation in a screening programme
The Screening programme
- There should be evidence from high quality Randomised Controlled Trials that the screening programme is effective in reducing mortality or morbidity
- Where screening is aimed solely at providing information to allow the person being screened to make an "informed choice" (eg. Down's syndrome, cystic fibrosis carrier screening), there must be evidence from high quality trials that the test accurately measures risk
- The information that is provided about the test and its outcome must be of value and readily understood by the individual being screened
- There should be evidence that the complete screening programme (test, *diagnostic procedures, treatment/ intervention) is clinically, socially and ethically acceptable to health professionals and the public
- The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment)
- The opportunity cost of the screening programme (including testing, diagnosis and treatment, administration, training and quality assurance) ) should be economically balanced in relation to expenditure on medical care as a whole (ie. value for money)
- There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards
- Adequate staffing and facilities for testing, diagnosis, treatment and programme management should be available prior to the commencement of the screening programme
- All other options for managing the condition should have been considered (e.g. improving treatment, providing other services), to ensure that no more cost effective intervention could be introduced or current interventions increased within the resources available
- Evidence-based information, explaining the consequences of testing, investigation and treatment, should be made available to potential participants to assist them in making an informed choice
- Public pressure for widening the eligibility criteria for reducing the screening interval, and for increasing the sensitivity of the testing process, should be anticipated
- Decisions about these parameters should be scientifically justifiable to the public
Effectiveness of screening
- The likelihood of the test correctly identifying cancer: If the test is not sensitiveSensitivity and specificitySensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
, then it may miss cancers. If the test is not specificSensitivity and specificitySensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
, then it may wrongly indicate cancer in a healthy person. All cancer screening tests produce both false positives and false negatives, and most produce more false positives. Experts consider the rate of errors when making recommendations about which test, if any, to use. A test may work better in some populations than others. The positive predictive valuePositive predictive valueIn statistics and diagnostic testing, the positive predictive value, or precision rate is the proportion of subjects with positive test results who are correctly diagnosed. It is a critical measure of the performance of a diagnostic method, as it reflects the probability that a positive test...
is a calculation of the likelihood that a positive test result actually represents cancer in a given individual, based on the results of people with similar risk factors.
- Possible harms from the screening test itself: Some types of screening tests are potentially harmful to the human body. There is a very small chance, for example, that the x-rays used in mammography could cause cancer in a healthy person.
- Possible harms from follow-up procedures: If the screening test is positive, further diagnostic testing is normally done, such as a biopsyBiopsyA biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
of the tissue. If the test produces many false positives, then many people will undergo needless medical procedures, some of which may be dangerous.
Breast cancer
There is general agreement in the scientific community that breast screening reduces mortality from the disease.There is some controversy however about the number of lives saved by breast screening and the number of cancers diagnosed and treated that would not have caused any health problems in the participants' lifetime, sometimes known as over-diagnosis and over-treatment.
Non-invasive breast cancers, or Ductal Carcinoma in Situ, sometimes progress to invasive cancer but sometimes do not. Since doctors cannot usually distinguish which DCIS will go on to invasive cancer, most are treated. This is where over-treatment can arise.
The U.S. Preventive Services Task Force
U.S. Preventive Services Task Force
The U.S. Preventive Services Task Force is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services." The task force, a panel of primary care physicians and...
(USPSTF) recommends populationscreening mammography once for every two years for all women aged 50—74, with decisions about screening younger and older women being determined by consideration of the individual's risk factors and the benefits and harms of screening. They do not recommend either breast self-examination
Breast self-examination
Breast self-examination is a screening method used in an attempt to detect early breast cancer. The method involves the woman herself looking at and feeling each breast for possible lumps, distortions or swelling....
or clinical breast examination. Their recommendation is similar to the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
's, and less aggressive than most North American organizations.
Cervical cancer
Cervical screening is highly effective at detecting and preventing cervical cancer.The U.S. Preventive Services Task Force
U.S. Preventive Services Task Force
The U.S. Preventive Services Task Force is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services." The task force, a panel of primary care physicians and...
(USPSTF) strongly recommends cervical cancer
Cervical cancer
Cervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages...
screening in American women who are sexually active and have a cervix
Cervix
The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...
at least until the age of 65, usually every three years. Their recommendation is typical of professional organizations and other government agencies in the US and Canada.
Bowel cancer
Prostate cancer
When screening for prostate cancerProstate 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...
, the PSA
Prostate specific antigen
Prostate-specific antigen also known as gamma-seminoprotein or kallikrein-3 is a glycoprotein that in humans is encoded by the KLK3 gene. KLK3 is a member of the kallikrein-related peptidase family that are secreted by the epithelial cells of the prostate gland...
test may detect small cancers that would never become life threatening, but once detected will lead to treatment. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. Follow up procedures used to diagnose prostate cancer (prostate biopsy
Prostate biopsy
Prostate biopsy is a procedure in which small samples are removed from a man's prostate gland to be tested for the presence of cancer. It is typically performed when the scores from a PSA blood test rise to a level that is associated with the possible presence of prostate cancer.The procedure,...
) may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence
Urinary incontinence
Urinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
(inability to control urine flow) and erectile dysfunction
Erectile dysfunction
Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....
(erections inadequate for intercourse).
Lung Cancer
According to the U.S. Preventive Services Task ForceU.S. Preventive Services Task Force
The U.S. Preventive Services Task Force is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services." The task force, a panel of primary care physicians and...
(USPSTF), there is insufficient evidence to recommend for or against screening for 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...
.
Recent research suggests that screening heavy smokers may be effective.
There is insufficient evidence to recommend for or against screening for skin cancer
Skin cancer
Skin neoplasms are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancer, squamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises...
, and oral cancer
Oral cancer
Oral cancer is a subtype of head and neck cancer, is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic structure, such as the...
. Routine screening is not recommended for bladder cancer
Bladder cancer
Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
, testicular cancer
Testicular cancer
Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system.In the United States, between 7,500 and 8,000 diagnoses of testicular cancer are made each year. In the UK, approximately 2,000 men are diagnosed each year. Over his lifetime, a man's risk of...
, ovarian cancer
Ovarian cancer
Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....
, and pancreatic cancer
Pancreatic cancer
Pancreatic cancer refers to a malignant neoplasm of the pancreas. The most common type of pancreatic cancer, accounting for 95% of these tumors is adenocarcinoma, which arises within the exocrine component of the pancreas. A minority arises from the islet cells and is classified as a...
.
According to the U.S. Preventive Services Task Force
U.S. Preventive Services Task Force
The U.S. Preventive Services Task Force is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services." The task force, a panel of primary care physicians and...
(USPSTF), there is insufficient evidence to recommend for or against screening for prostate cancer in men under 75. Routine screening is not recommended for prostate cancer in men over 75. Most North American medical groups recommend individualized decisions about screening, taking into consideration the risks, benefits, and the patients' personal preferences.
Whole body imaging
Use of medical imagingMedical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
to search for cancer in people without clear symptoms is similarly marred with problems. There is a significant risk of detection of what has been recently called an incidentaloma
Incidentaloma
In medicine, an incidentaloma is a tumor found by coincidence without clinical symptoms or suspicion. It is a common problem: up to 7% of all patients over 60 may harbor a benign growth, often of the adrenal gland, which is detected when diagnostic imaging is used for the analysis of unrelated...
- a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations.
External links
- NHS cancer screening programmes
- Screening for cancer, Cancer Research UKCancer Research UKCancer Research UK is a cancer research and awareness charity in the United Kingdom, formed on 4 February 2002 by the merger of The Cancer Research Campaign and the Imperial Cancer Research Fund. Its aim is to reduce the number of deaths from cancer. As the world's largest independent cancer...
- Cancer screening overview, National Cancer InstituteNational Cancer InstituteThe National Cancer Institute is part of the National Institutes of Health , which is one of 11 agencies that are part of the U.S. Department of Health and Human Services. The NCI coordinates the U.S...
- Cancer Screening, eMedicineHealth
- ColonCancerCheck including fact sheets in 24 languages at Ontario Ministry of Health and Long-Term Care
- http://www.scotland.gov.uk/Topics/Health/health/cancer/Cancer-Screening/criteria
- How screening recommendations have changed over time from the American Cancer SocietyAmerican Cancer SocietyThe American Cancer Society is the "nationwide community-based voluntary health organization" dedicated, in their own words, "to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and...