Although risks and benefits of cancer screening tests are carefully considered during the development of screening recommendations, it is important to note that screening tests are medical procedures and carry potential harms. It is thus concerning that a recent study found that not all cancer screening recommendations and guidelines included potential harms associated with screening tests. Researchers reviewed 33 commonly used screening guidelines from various expert panels and found that some harms were not mentioned at all, while others were mentioned only briefly (279). It is vital that the information about benefits and potential harms of cancer screening is clearly and easily available so that people can make an informed and shared decision in consultation with their health care providers (see Sidebar 19, p. 57). Benefits and Potential Harms of Cancer Screening The U.S. Preventive Services Task Force (USPSTF) or other professional societies focused on cancer care meticulously review the available scientific evidence to weigh benefits of screening for a specific cancer type against potential harms before issuing final screening guidelines. Because no individual test is perfect, USPSTF recommendations include a letter grade; screening tests that are recommended with a Grade A or B have been shown to have benefits that outweigh potential harms from screening (see Sidebar 20, p. 59). It is important to note that harms from a cancer screening test are rare. Furthermore, the benefits-to-potential-harms ratio can vary for different population groups as well as for individuals based on age, gender, and existing medical conditions among other factors. BENEFITS Reduced cancer mortality If a screening test detects precancerous lesions or cancer at an early stage of development, it may increase the likelihood that a patient can be successfully treated, thus reducing the risk of dying from cancer. Reduced cancer incidence If a screening test detects precancerous lesions, removing these lesions can reduce, or even eliminate, an individual’s risk of ever developing the screened cancer. Reduced likelihood of advanced disease If a screening test detects cancer at an early stage of development, it may reduce an individual’s risk of being diagnosed with the screened cancer at an advanced stage, thus making treatment more successful and avoiding more complex treatment regimens. POTENTIAL HARMS Adverse events Screening tests could carry risks of harm. For example, colonoscopy can potentially cause a cut in the wall of the colon in rare cases. Anxiety Screening tests could cause fear, worry, and/or anxiety in individuals who are eligible for cancer screening and may not have the disease. False-negative test results Screening tests could sporadically give negative results in individuals who are not free from the screened cancer, leading to missed opportunities for early treatment. False-positive test results Screening tests could give false-positive results in individuals who do not have the screened cancer, leading to additional unnecessary medical procedures, treatments, and anxiety. Overdiagnosis and overtreatment Screening tests could sometimes overdiagnose, i.e., detect precancerous lesions or cancers that may not go on to cause symptoms and threaten life, leading to overtreatment with its own potential harms. Incidental findings Screening tests might find an unrelated medical issue—such as finding an unrelated heart problem— and require follow-up tests or procedures which also have risks. SIDEBAR 19 Screening for Early Detection AACR Cancer Progress Report 2023 57
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