Cancer Screening

About Cancer Screening

Cancer screening involves looking for cancer in a person without any symptoms. Screening tests are done when you have no cancer symptoms.  It is important to understand that cancer screening is recommended often because of age, gender or other risk factors and does not mean you have cancer.  

The aim of screening tests is to detect cancer at an early stage, before symptoms appear. When precancerous cells or cancer is detected early, it may be easier to treat or cure. In most cases, by the time a person has symptoms, the cancer may be advanced and have spread. This would make treatment success or cure more difficult.

There are many different types of screening tests. Some screening tests do come with risks and can cause complications. There is also the possibility of a false-positive or false-negative test result. It is also important to understand that though cancer screening aims to improve survival, finding cancer may not necessarily improve the person’s health or help the person live longer.

Screening tests
  • Screening tests include the following:
  • Medical history and physical examination
  • Laboratory tests: Including tissue samples, blood, urine and stool
  • Imaging studies: Including ultrasound, Chest X-rays, 
  • Genetic tests
  • Endoscopy
Screening tests have risks

It is important to know the risks of any screening test and whether the test has been proven to decrease the chance of dying from cancer. For example, colon cancer screening using sigmoidoscopy or colonoscopy can cause bleeding or perforation in the lining of the colon.

False-positive test results

A false positive test result occurs when a screening test result is abnormal even though there is no cancer. This can cause anxiety and may lead to over-investigation, which also carries risks.

False-negative test results

False negative test results can arise even though there is actually cancer present. False-negative test results can lead to delays seeking medical diagnosis and treatment even if symptoms are present.

Screening and finding the cancer

Screening and finding the cancer does not necessarily improve the person’s health or prolong life in all cases.

Patients need to be aware of lead-time bias and that screening in itself may not necessarily result in improved survival. Patients diagnosed with cancer can also pass on due to other causes other than cancer.

Informed and Shared Decision-Making?

It is important that you understand the risks and benefits of screening tests and make an informed choice to proceed with the test. Discuss the test with your doctor. Your doctor should talk to you about how the procedure is conducted and what the risks and benefits are and include you in the decision about whether to proceed. This is called informed and shared decision-making.

What Are the Goals of Screening Tests?

A good screening test should achieve the following:

  • Help to then diagnose cancer before symptoms appear.
  • Screen for cancers that are easier to treat and cure when diagnosed early.
  • Have a low false-negative test and false-positive test probability
  • Decrease the chance of dying from cancer.
Screening tests are not meant to diagnose cancer.

Screening tests in themselves  may not diagnose cancer. If a screening test result is abnormal, more tests may be done to check for cancer. For example, a positive faecal occult blood test may then lead to a colonoscopy for colon cancer screening. Diagnostic tests usually involve a biopsy, in which cells or tissues are extracted so a pathologist can look at them under a microscope for cancer cells.

Who Needs to Be Screened?

Screening tests are usually indicated in individuals who may carry a  higher risk for certain cancers. A risk factor is anything that increases the chance of cancer, though it does not mean one will definitely develop cancer. However, People who have a high risk of cancer may need to be screened more often or at an earlier age than other people.

Risk factors include:
  • Age
  • Gender
  • Previous cancer.
  • Family history of cancer.
  • Genetic mutations
  • Exposure to cancer-causing agents such as tobacco smoke or chemicals such as asbestos.
Does Screening Definitely Help People Live Longer?

Cancers diagnosed at an early stage (before symptoms appear) hopefully helps decrease the chance of dying from those cancers, but this doesn’t always happen.

The chance of recovery depends on the stage or how far the cancer has spread to the rest of the body. Cancers that are diagnosed at earlier stages generally have a better chance at treatment or cure. However, this isnt always the case.