About cancer screening
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Cancer screening is a systematic examination of an apparently healthy population group. The goal is to detect risk factors, precancerous changes, or early-stage cancer before symptoms appear.
About organized cancer screening
Early detection and diagnosis increase the chances that treatment will be effective and lead to a better prognosis.
An organized cancer screening program aims to:
reduce mortality and morbidity from the specific type of cancer through early detection and treatment (as with mammography screening and bowel cancer screening).
reduce the incidence and mortality of the specific type of cancer by identifying and treating precancerous changes (as with cervical or bowel cancer screening).
Population screening is offered to a large number of people, usually based on their age or sex. Targeted screening aims to identify individuals at higher risk for a condition, for example due to lifestyle factors or genetic predisposition.
The methods used in cancer screening are based on different technologies depending on the type of cancer. These may include imaging, cell samples, antibodies, and other biochemical markers.
For simplicity, we will use the general term screening test throughout this text.
Screening versus Diagnostic Testing
Screening is not the same as diagnostic testing. Diagnostic tests are performed to confirm or rule out disease in individuals who already have symptoms.
A cancer screening program, on the other hand, targets people in a defined population group who do not have symptoms, and invites them or sends reminders to get tested.
A screening test cannot determine whether a person has cancer, but it can detect findings that indicate the need for further testing or follow-up.
Cancer Screening Programs in Norway
There are currently three organized national cancer screening programs in Norway: screening for breast cancer, cervical cancer, and colorectal cancer. These programs are managed and quality assured by the Cancer Registry of Norway, which is part of the Norwegian Institute of Public Health.
The Ministry of Health and Care Services (HOD) holds overall responsibility for the national cancer screening programs and makes political decisions regarding the establishment of new programs and major changes to existing ones.
A joint national steering committee for the screening programs has been established and is led by the Norwegian Directorate of Health. The committee's mandate is to discuss, advise, and make decisions on matters related to the national screening programs.
In February 2025, HOD launched a new national cancer strategy, which includes plans to establish two new organized screening programs—for lung cancer and prostate cancer.
However, launching new programs requires thorough assessments and health economic analyses. The Directorate of Health has been tasked with conducting these assessments.
Criteria for Cancer Screening Programs
Cancer screening aims to both prevent and detect cancer at an early stage, so that treatment can be effective and public health can be improved.
However, this does not mean that all types of cancer should or can be screened for in an organized way. Before a cancer screening program is established, several criteria must be evaluated. These criteria relate both to the disease itself and to the methods and systems intended for use.
In 1968, the World Health Organization (WHO) published a list of ten criteria that a country should consider before introducing screening. In 2014, the Norwegian Directorate of Health added six new points to this original list. When health authorities evaluate the potential implementation of a new screening program, they must assess it against these criteria using up-to-date scientific evidence.
Benefits and Drawbacks of Organized Cancer Screening
Cancer screening has both benefits and drawbacks that must be continuously monitored to ensure the intended effects are achieved.
A screening program should only be recommended and implemented if evidence shows that the process—including follow-up tests and treatment—provides more benefit than harm and is cost-effective.
There is an ethical obligation to ensure high quality, continuous improvement, and support for research to optimize screening programs.
Potential benefits of organized cancer screening
Detection of cancer at an early stage: Reduces the risk of severe disease and death from cancer.
Less burdensome treatment: Early treatment may be less extensive, with fewer side effects and long-term consequences, leading to improved quality of life for patients during and after treatment. This also saves resources for the healthcare system and society.
Reduced incidence: By identifying and treating precancerous changes, screening can help prevent certain cancers from developing.
Reduced mortality: Organized screening programs have been shown to reduce mortality for certain cancer types, such as breast cancer, cervical cancer, and colorectal cancer.
Systematic monitoring and quality assurance: Organized programs follow established guidelines and quality standards, enabling continuous monitoring of the quality of screening and follow-up.
Evaluation and research: Data from screening programs contribute to research and new knowledge in cancer prevention and treatment, which can improve future programs and therapies.
Equitable access to screening: Everyone in the target population receives the same offer, which can help reduce social inequalities in health.
Potential drawbacks of screening
Overdiagnosis and overtreatment: Screening can detect cancers that would never have caused symptoms or developed into serious illness during a person's lifetime. This can lead to unnecessary treatment that may be physically or emotionally taxing.
False positive and false negative results: False positives may cause anxiety and lead to unnecessary investigations, while false negatives can give a false sense of security and delay necessary treatment.
Physical and psychological burdens: The screening process can be uncomfortable (e.g., mammography or cervical sampling). Further investigations such as colonoscopy may involve risks of complications. Waiting for results can also cause stress and anxiety.
Resource use: Organized screening programs allocate healthcare resources to examine people who are initially healthy, which can increase pressure on the healthcare system.
There may also bespecific disadvantages related to the tests and methods used in the different screening programs. More information is available on the individual program websites.
Overview of the Steps in a Screening Program
A cancer screening program is a process, not just a single test. It consists of several steps and functions as a cycle, where individuals with a negative or normal screening test are invited to screen again after a set interval.
Those who are found to have precancerous changes, cancer, or other findings requiring follow-up exit the screening cycle and enter a diagnostic and/or treatment pathway.