The examples and perspective in this article deal primarily with the Western world and do not represent a worldwide view of the subject.(March 2024) |
Cancer screening | |
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Purpose | detection of cancer prior to onset of symptoms (via several tests/imaging) |
The objective of cancer screening is to detect cancer before symptoms appear, involving various methods such as blood tests, urine tests, DNA tests, and medical imaging. [1] [2] The purpose of screening is early cancer detection, to make the cancer easier to treat and extending life expectancy. [3] In 2019, cancer was the second leading cause of death globally; more recent data is pending due to the COVID-19 pandemic. [4]
Universal screening, also known as mass screening or population screening, involves the screening of individuals within certain age and gender groups, aiming to screen the population for particular cancers or cancer risk factors. [5] Selective screening, also known as targeted screening, identifies individuals with a higher risk of developing cancer, including individuals with a family history (genetic risk) of cancer or individuals engaging in high-risk behaviors such as smoking. [5]
The act of cancer screening plays a pivotal role in both preventing cancer and providing early diagnosis, contributing to increased success rates in treatment and ultimately extending life expectancy. [6] Controversy arises when it is not clear if the benefits of the screening outweigh the risks associated with the screening procedure, as well as the subsequent diagnostic tests and cancer treatments. [7] Cancer screening is susceptible to producing both false negative and false positive results, underlining the importance of considering the possible errors in the screening process. [8] Additionally, cancer screening can lead to overtreatment if the screening identifies a tumor that is ultimately benign (non-cancerous). [6]
Early detection of cancer is the main advantage of cancer screening, it gives the patient a better chance of surviving or even preventing the cancer. Screening can also help relieve the public burden cancer has on society both financially and socially. [9] The EU's Beating Cancer Plan wishes to make sure that 90% of the population with sufficient risk is screened for breast, cervical and colorectal cancer; around 1.3 million people die from cancer in the EU each year. [9]
Several factors are considered to determine whether the benefits outweigh the associated risks and costs of cancer screening. [1] Cancer screening trials have demonstrated only a minimal decline in cancer related deaths, and the evaluation of risks to benefits remains an important in determining the overall effectiveness of the cancer screening program. [10]
To detect cancer at an early stage, all eligible people need to participate in screenings. [17] However, certain barriers affect attendance rates among disadvantaged individuals, such as those on low incomes, those with mental health disorders, and ethnic minorities. [17]
A 2019 study indicated that individuals with mental health disorders are nearly 25% less likely to attend cancer screening appointments. [18] Among them, women with schizophrenia have the lowest screening rates. [18] Even those with common mood disorders, such as anxiety and depression, are less likely to attend compared the general population. [18] The lower attendance rates are believed to contribute to the earlier mortality of people with mental health disorders. [18]
In 2019, a study indicated that women with mental health disorders in Northern Ireland were less likely to participate in screening for breast cancer in comparison to women without mental health disorders. [19] The documented attendance rate persisted even after accounting for variables, such as marital status and social deprivation. [19]
A study published in 2020 reported that individuals from minority ethnic communities are also less likely to participate cancer screening initiatives. [20] [21] The study showed that British-Pakistani women encountered cultural and language barriers and were not aware that breast cancer screening do not take place in a female-only environment. [20] [21] In the UK, women of South Asian heritage display the lowest likelihood of participating in breast cancer screening. [20] [21] Further studies is still necessary to identify the specific barriers for the different South Asian communities. [20] [21]
Deprivation has been recognised as an additional factor contributing to the decrease of individuals attending cancer screening. [22] A UK study indicated that making cancer screening easily accessible increased attendance. [22] Providing mobile screening units parked in supermarket car parks, for example in the poorer areas of Manchester, was a viable approach for offering lung checks to high-risk groups (such as smokers). [22] A simple test measured obstruction to the airflow in and out of the lungs. [22] A third of the tests revealed airflow obstruction, indicating chronic obstructive pulmonary disease (COPD), a risk factor for lung cancer and various other health conditions. [22]
Breast cancer is the most common cancer for women. [23] Screening is done to detect the disease early in asymptomatic women, in an attempt to achieve an earlier diagnosis and lower mortality. Different screening tests are used for breast cancer screening, including clinical and self-examination of the breasts, mammography, and magnetic resonance imaging (MRI). Mammography is the standard method for breast cancer screening. This method is reported to give a 40% reduction in the risk of dying from the disease. [24] Breasts with less fat and more fibrous tissue are known as dense breasts, they are a risk factor for breast cancer. The tissue makes it harder to find tumors while doing a mammogram, therefore MRI screening is proposed to supplement the mammogram in these patients. [24]
Like other cancers there are advantages and disadvantages to screening for breast cancer, with risks of harm by overdiagnosis, a possibility of radiation-induced cancer and false positives. From organized programmes it is estimated that 20% of women with 10 screens from ages 50 to 70 will get a false positive result, less than 5% of these cases will result in further invasive treatment. [24] Radiation-induced cancer from screening with mammography has been approximated to be around 1 to 10 per 100,000 women, which is lower than the estimate of death from breast cancer itself. [24]
Mutations of the genes BRCA1 and BRCA2 can increase the risk of breast cancer in the patients lifetime. In the US, risk factors for breast cancer like the BRCA gene and age are taken into consideration to decide if a screening test is needed and if so which is best for the person. [25]
Many European countries have organized population-level screening programmes for breast cancer. In 2022, the European Commission's Scientific Advice Mechanism concluded that women should be screened for breast cancer earlier, starting while in their mid 40s. [26]
Cervical cancer is the fourth most common cancer for women with an estimated 340,000 deaths according to the World Health Organization (WHO). [27] HPV disease is the leading cause of cervical cancer, therefore making the HPV vaccine the primary prevention measure for the cancer. Screening with the Papanicolaou (Pap) test is consequently the second measure of prevention. [27] The test identifies cells that are precancerous, and are often credited for the reduced mortality. [28]
WHO encourage implementing population-based screening programs. There is a considerable range in the recommended age at which to begin screening around the world. The US does not follow a nation-wide program, and guideline recommendations differ, with some states recommend commencing screening at age 21 and others at 25; the intervals for testing also very, with intervals ranging from 3–5 years. The EU has guidelines for its member states when it comes to cancer screening, but they are not obliged to follow them as they are merely for assistance; it recommends population-based screening programs from age 30 using HPV tests with 5 year intervals. [27]
In 2022, the European Commission's Scientific Advice Mechanism concluded that improved cervical cancer screening, combined with widespread HPV vaccination, presented an opportunity to eliminate cervical cancer in Europe. [29]
Screening for colorectal cancer, if done early enough, is preventive, seeing as benign lumps called polyps in the colon and rectum are the start to almost all cases of colon cancer. These polyps can be identified and removed by screening tests like a colonoscopy, in which the whole colon is visible. If the cancer develops then a colectomy is required, this is a more intrusive surgery. Other treatment methods are needed if the cancer has started to spread more. Early diagnosis of the cancer can remove the need for more intrusive treatments and patients can be healed. [30] [31]
The US Preventive Services Task Force recommends all adults between the ages 50–75 to be screened for colorectal cancer, they also recommend adults between the ages 45–49 be screened as well. For adults 76–85 they recommend offering clinically selective screenings, where patient preference, overall health and history with screening is taken into consideration when deciding where to do a screening. This is due to evidence that there is overall little benefit in screening this group. Stool tests, sigmoidoscopy and colonoscopy are the most accepted screening tests for colorectal cancer in the US. [31]
Colorectal cancer screening programmes are widespread in Europe. In England, adults are screened biennially between ages 60–74, [32] and recently extended to ages 50–74. They are screened via fecal immunochemical test (FIT), that is sent home to the individual. However the program currently has a high threshold in which a big proportion of patients with high-risk polyps are missed and not investigated further. [33] [34] In March 2022, the European Commission's Scientific Advice Mechanism recommended age, sex, and previous screening results be used when deciding screenings frequency to improve diagnosis. [26]
Prostate cancer was estimated to be the second leading cause of death by cancer in the US in 2018. [35] There are different methods used in screening for prostate cancer prostate biopsy, prostate-specific antigen testing (PSA), and digital rectal examination (DRE). In the DRE the examiner inserts a finger in the rectum of the patient and examines size and irregularities in the prostate gland. During PSA screening, blood is tested for the protein, prostate-specific antigen, secreted from the prostate gland, levels over 4 ng/mL are indicators for further analysis. At this cutoff point the patient has a 25% chance of having the disease. [36] Because the antigen is prostate specific it can also be elevated by other concerns in the prostate, like prostatitis and benign enlargements of the gland. A prostate biopsy is then performed to evaluate further diagnosis and treatment. [36]
When PSA screening began in the 1980s, cases of prostate cancer rose by 26% between 1986-2005, with the most affected age group being men under the age of 50. [37] Prostate cancer is a heterogeneous disease, and the cancer will grow aggressively in approximately 1 in 3 cases. Therefore there is a risk of overdiagnosing and overtreating, this has been subject to debate for many years. [26]
The US Preventative Service Task Force have previously recommended against PSA testing in a systematic manner because of the overdiagnosis risks. In recent years recommendations like these are being revised, as new methods of screening are advancing, like MRI scanning as a secondary assessment to the PSA test. More research needs to be done in this area, to identify who has the most benefit of screening. [9]
As of 2020, lung cancer accounted for 18.4% of cancer mortalities worldwide. Because of late disgnosis only 15% of patients will live more than 5 years after their diagnosis. [38] The NELSON trial concluded that with low-dose computed tomography (LDCT) performed on high-risk populations, there is a significantly lower mortality than with no screening at all. [38]
Smoking is the leading cause of lung cancer, and is the cause of death in 55% of women and 70% of men with lung cancer. [39] The US Preventative Service Task Force revised the recommendations for lung cancer screening in 2021, where annual LDCT is recommended for adults between the ages 50 and 80, who either currently smoke or have a history of smoking 20 or more packs yearly, in the past 15 years. They also ceased the recommendation of annual screening for individuals who have refrained from smoking the last 15 years and those who have new medical issues that already reduce life expectancy. These new recommendations have increased the number of people qualified for lung cancer screening by 86%. [40]
Similarly, in March 2022, the European Commission's Scientific Advice Mechanism recommended lung screening for current and ex-smokers, combined with ongoing smoking cessation programs. [29]
Early detection of pancreatic cancer biomarkers was accomplished using SERS-based immunoassay approach. [41] A SERS-base multiplex proteinbiomarker detection platform in a microfluidic chip to detect is used to detect several protein biomarkers to predict the type of disease and critical biomarkers and increase the chance of diagnosis between diseases with similar biomarkers (prostate cancer, ovarian cancer, and pancreatitis). [42] It is generally agreed that general screening of large groups for pancreatic cancer is not at present likely to be effective, and outside clinical trials there are no programmes for this. The European Society for Medical Oncology recommends regular screening with endoscopic ultrasound and MRI/CT imaging for those at high risk from inherited genetics, [43] in line with other recommendations, [44] [45] which may also include CT. [44] For screening, special CT scanning procedures may be used, such as multiphase CT scan. [46]
The US Preventive Services Task Force (USPSTF) in 2013 found that evidence was insufficient to determine the balance of benefits and harms of screening for oral cancer in adults without symptoms by primary care providers. [47] The American Academy of Family Physicians comes to similar conclusions while the American Cancer Society recommends that adults over 20 years who have periodic health examinations should have the oral cavity examined for cancer. [47] The American Dental Association recommends that providers remain alert for signs of cancer during routine examinations. [47] Oral cancer screening is also recommended by some groups of dental hygienists. [48]
USPSTF have recommendations for breast, cervical, colorectal and lung cancer as these have evidence-based screening methods. For the general population other cancers don't have recommended screenings, but for people with risk factors known to be associated with a specific cancer there are screenings available. [49]
Full body CT scans is a type of medical imaging utilized to search for cancer in individuals without clear symptoms. CT scans can pose challenges, especially exposure to ionizing radiation. [50] However, magnetic resonance imaging (MRI) scans are not associated with a radiation risk, and MRI scans are being evaluated for their use in cancer screening. [51] There is a significant risk of detecting incidentalomas - benign lesions that might be misinterpreted as cancer and put patients at potential risk by undergoing unnecessary follow-up procedures. [52]
In 2023 the FDA approved the first blood test for the detection of cancer, which identifies DNA variants in 47 genes associated with an elevated risk of hereditary cancer. [53] [54] This test is manufactured by Invitae. [53] Other tests on the market are multi-cancer early detection (MCED). [55] These are distinct from hereditary cancer tests since they detect the presence of cancer through circulating tumor DNA in the blood. [55] More MCED tests are currently in development. The tests include,
As of 2023 multiple major clinical studies are undergoing for the assessment of more blood tests. [58] [57] The current generation of blood tests exhibit false positive rates ranging between 0.5-1%. [57] The risk of false positives from population screening has to be weighed against the prevalence of cancer in the screened population.
Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a red or scaly patch of skin. In those with distant spread of the disease, there may be bone pain, swollen lymph nodes, shortness of breath, or yellow skin.
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. While these symptoms may indicate cancer, they can also have other causes. Over 100 types of cancers affect humans.
Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum. Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, abdominal pain and fatigue. Most colorectal cancers are due to old age and lifestyle factors, with only a small number of cases due to underlying genetic disorders. Risk factors include diet, obesity, smoking, and lack of physical activity. Dietary factors that increase the risk include red meat, processed meat, and alcohol. Another risk factor is inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis. Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases. It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancerous.
Mammography is the process of using low-energy X-rays to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through detection of characteristic masses or microcalcifications.
Prostate-specific antigen (PSA), also known as gamma-seminoprotein or kallikrein-3 (KLK3), P-30 antigen, is a glycoprotein enzyme encoded in humans by the KLK3 gene. PSA is a member of the kallikrein-related peptidase family and is secreted by the epithelial cells of the prostate gland in men and the paraurethral glands in women.
Digital rectal examination (DRE), also known as a prostate exam, is an internal examination of the rectum performed by a healthcare provider.
In a physical examination, medical examination, clinical examination, or medical checkup, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the patient's medical history followed by an examination based on the reported symptoms. Together, the medical history and the physical examination help to determine a diagnosis and devise the treatment plan. These data then become part of the medical record.
A stool test is a medical diagnostic technique that involves the collection and analysis of fecal matter. Microbial analysis (culturing), microscopy and chemical tests are among the tests performed on stool samples.
Screening, in medicine, is a strategy used to look for as-yet-unrecognised conditions or risk markers. This testing can be applied to individuals or to a whole population without symptoms or signs of the disease being screened.
Overdiagnosis is the diagnosis of disease that will never cause symptoms or death during a patient's ordinarily expected lifetime and thus presents no practical threat regardless of being pathologic. Overdiagnosis is a side effect of screening for early forms of disease. Although screening saves lives in some cases, in others it may turn people into patients unnecessarily and may lead to treatments that do no good and perhaps do harm. Given the tremendous variability that is normal in biology, it is inherent that the more one screens, the more incidental findings will generally be found. For a large percentage of them, the most appropriate medical response is to recognize them as something that does not require intervention; but determining which action a particular finding warrants can be very difficult, whether because the differential diagnosis is uncertain or because the risk ratio is uncertain.
Prostate cancer screening is the screening process used to detect undiagnosed prostate cancer in men without signs or symptoms. When abnormal prostate tissue or cancer is found early, it may be easier to treat and cure, but it is unclear if early detection reduces mortality rates.
Lung cancer screening refers to cancer screening strategies used to identify early lung cancers before they cause symptoms, at a point where they are more likely to be curable. Lung cancer screening is critically important because of the incidence and prevalence of lung cancer. More than 235,000 new cases of lung cancer are expected in the United States in 2021 with approximately 130,000 deaths expected in 2021. In addition, at the time of diagnosis, 57% of lung cancers are discovered in advanced stages, meaning they are more widespread or aggressive cancers. Because there is a substantially higher probability of long-term survival following treatment of localized (60%) versus advanced stage (6%) lung cancer, lung cancer screening aims to diagnose the disease in the localized stage.
The United States Preventive Services Task Force (USPSTF) 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 volunteer panel of primary care clinicians with methodology experience including epidemiology, biostatistics, health services research, decision sciences, and health economics, is funded, staffed, and appointed by the U.S. Department of Health and Human Services' Agency for Healthcare Research and Quality.
Breast cancer screening is the medical screening of asymptomatic, apparently healthy women for breast cancer in an attempt to achieve an earlier diagnosis. The assumption is that early detection will improve outcomes. A number of screening tests have been employed, including clinical and self breast exams, mammography, genetic screening, ultrasound, and magnetic resonance imaging.
Molecular breast imaging (MBI), also known as scintimammography, is a type of breast imaging test that is used to detect cancer cells in breast tissue of individuals who have had abnormal mammograms, especially for those who have dense breast tissue, post-operative scar tissue or breast implants.
Positron emission mammography (PEM) is a nuclear medicine imaging modality used to detect or characterise breast cancer. Mammography typically refers to x-ray imaging of the breast, while PEM uses an injected positron emitting isotope and a dedicated scanner to locate breast tumors. Scintimammography is another nuclear medicine breast imaging technique, however it is performed using a gamma camera. Breasts can be imaged on standard whole-body PET scanners, however dedicated PEM scanners offer advantages including improved resolution.
Dynamic angiothermography (DATG) is a technique for the diagnosis of breast cancer. This technique, though springing from the previous conception of thermography, is based on a completely different principle. DATG records the temperature variations linked to the vascular changes in the breast due to angiogenesis. The presence, change, and growth of tumors and lesions in breast tissue change the vascular network in the breast. Consequently, through measuring the vascular structure over time, DATG effectively monitors the change in breast tissue due to tumors and lesions. It is currently used in combination with other techniques for diagnosis of breast cancer. This diagnostic method is a low-cost one compared with other techniques.
Overscreening, also called unnecessary screening, is the performance of medical screening without a medical indication to do so. Screening is a medical test in a healthy person who is showing no symptoms of a disease and is intended to detect a disease so that a person may prepare to respond to it. Screening is indicated in people who have some threshold risk for getting a disease, but is not indicated in people who are unlikely to develop a disease. Overscreening is a type of unnecessary health care.
Cancer prevention is the practice of taking active measures to decrease the incidence of cancer and mortality. The practice of prevention depends on both individual efforts to improve lifestyle and seek preventive screening, and socioeconomic or public policy related to cancer prevention. Globalized cancer prevention is regarded as a critical objective due to its applicability to large populations, reducing long term effects of cancer by promoting proactive health practices and behaviors, and its perceived cost-effectiveness and viability for all socioeconomic classes.
In medicine, breast imaging is a sub-speciality of diagnostic radiology that involves imaging of the breasts for screening or diagnostic purposes. There are various methods of breast imaging using a variety of technologies as described in detail below. Traditional screening and diagnostic mammography uses x-ray technology and has been the mainstay of breast imaging for many decades. Breast tomosynthesis is a relatively new digital x-ray mammography technique that produces multiple image slices of the breast similar to, but distinct from, computed tomography (CT). Xeromammography and galactography are somewhat outdated technologies that also use x-ray technology and are now used infrequently in the detection of breast cancer. Breast ultrasound is another technology employed in diagnosis and screening that can help differentiate between fluid filled and solid lesions, an important factor to determine if a lesion may be cancerous. Breast MRI is a technology typically reserved for high-risk patients and patients recently diagnosed with breast cancer. Lastly, scintimammography is used in a subgroup of patients who have abnormal mammograms or whose screening is not reliable on the basis of using traditional mammography or ultrasound.