Dr. Bushra Cheema
WHAT IS SCREENING?
The term screening refers to the regular use of certain examinations or tests in people who do not have any symptoms of cancer, but are at high risk for developing certain types of cancer. For many types of cancer, progress in the area of cancer screening has offered promise for earlier detection, which often results in higher cure rates.
WHO SHOULD UNDERGO SCREENING TESTS FOR CANCER?
Not everyone needs to undergo regular screening for cancer. There are many factors that determine who should be screened. Over the years, researchers have established risk factors for certain types of cancer. Risk factors are certain characteristics or exposures that make people more likely to develop a type of cancer than other people who do not have those risk factors. Risk factors are different for different types of cancer.
There are two types of risk factors: genetic factors and non-genetic (environmental) factors. A genetic factor is an inherited, unchangeable trait. A non-genetic factor is a variable in a person’s environment, which can often be changed. Non-genetic factors may include diet, exercise, or exposure to other substances present in our surroundings. These non-genetic factors are often referred to as environmental factors. Some non-genetic factors play a role in facilitating the process of healthy cells turning cancerous (i.e. the correlation between smoking and lung cancer), while other cancers have no known environmental correlation, but are known to have a genetic predisposition. A genetic predisposition means that a person may be at higher risk for a certain cancer if a family member has that type of cancer.
WHAT TYPES OF SCREENING TESTS ARE AVAILABLE FOR CANCER?
There are many different types of screening tests designed to detect different types of cancer. Depending on the risk factors that are present, patients at a high risk for a certain type of cancer may be required to undergo any one of a number of tests. Examples of screening tests include imaging tests, such as CT scans or mammography; blood tests; or even surgical biopsy procedures. Some screening tests are non-invasive, such as diagnostic imaging, while other screening tests are more invasive, such as blood tests or colonoscopies. Screening tests are designed specifically to screen for certain types of cancer. For example, women at a high risk of developing breast cancer may need to undergo frequent mammograms, whereas individuals at a high risk for colon cancer will need to undergo colonoscopies.
Another type of screening test is predictive genetic testing. Modern technology has enabled us to identify relationships between specific genetic mutations and some cancers. As we continue to learn more about genetic mutations and identify additional mutations, the role of genetic testing will continue to grow.
Predictive genetic testing is used to determine if an individual has a genetic mutation that may predispose him/her to developing cancer. An accurate test will reveal a genetic mutation, but cannot guarantee that a person will develop cancer. Likewise, a genetic test that does not find a specific mutation cannot guarantee that an individual will not develop cancer. These tests only suggest that a person may or may not be at some level of increased risk.
WHAT IS THE PURPOSE OF DIAGNOSTIC TESTS?
Cancer patients undergo many different types of tests in order to accurately diagnose their disease, determine their prognosis, and monitor their cancer for progression or recurrence.
The term “diagnostic test” can be misleading, as these tests are not used only for diagnosing cancer, but also for monitoring cancer progression. There are many reasons for employing diagnostic tests depending on whether the disease is active or progressing, being treated, or in remission. Diagnostic tests may be used to:
Diagnose primary disease—identify the disease the first time it occurs
Identify cancer subtype—some cancers are divided into subtypes that are more or less aggressive; identification of a more aggressive subtype may influence the type of treatment proposed
Predict prognosis—test results may indicate chance of cure, based on outcomes of other patients with similar results
Direct treatment—cancer is many different diseases, all of which respond differently to various treatments. A diagnosis that accurately identifies the type of cancer and predicts prognosis will also help to identify the type of treatment that maximizes chance of cure
Evaluate response to treatment—some tests show whether the cancer is responding to treatment
Detect minimal residual disease—cancer cells that remain after treatment is completed are called MRD. Detection of MRD may indicate a higher likelihood of recurrence
Monitor remission or progression—if a cancer is in remission, frequent tests may help detect the cancer if it returns and/or determine whether it is progressing
Screen at-risk individuals—identifying abnormalities in cells or the DNA of cells of asymptomatic (healthy) individuals may indicate an increased risk (although not a certainty) of developing disease
Pathology Tests: Pathology tests involve microscopic evaluation of abnormal cells.
Diagnostic Imaging: Diagnostic imaging involves visualization of abnormal masses using high-tech machines that create images. Examples of diagnostic imaging include x-rays, computed tomography (CT) scans, positron emission tomography (PET) scans, magnetic resonance imaging (MRI), and combined PET/CT scans.
Blood Tests: Blood tests measure substances in the blood that may indicate how advanced the cancer is or other problems related to the cancer.
Tumor Markers: Tumor marker tests detect substances in blood, urine, or other tissues that occur in higher than normal levels with certain cancers.
Genomics: Special laboratory evaluation of DNA involves the identification of the genetic make-up-the DNA-of the abnormal cells.