By Dr. Sanjay Gupta, lead physician at the Binaytara Foundation Cancer Center
Cancer screening means checking your body for cancer before you have symptoms. This may involve blood test, Urine test, DNA test, other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harm.
Screening may be Universal screening or selective screening. Universal screening is done for everyone, usually within a specific age group, while selective screening identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.
Screening has both benefits as well as harm. The benefit is that, we can detect the cancer at early stage and cancer is curable if detected earlier. One third of cancers are curable if detected earlier. So there are lots of things that we can do to diagnose cancers in early stage. Similarly, there is harm of screening too. The test of screening may be false positive or false negative.
- False Positive: means test is positive in a non-cancerous patient. It increases the chance of unnecessary tests and invasive procedure to confirm the diagnosis.
- False Negative: means test is negative in a patient having cancer. As a result, there is delay in diagnosis of cancer.
So, the screening test should have high sensitivity and high specificity. Screening for cancer is controversial in cases when it is not yet known if the test actually saves lives. The controversy arises when it is not clear if the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments. Cancer screening is not indicated unless life expectancy is greater than five years and the benefit is uncertain over the age of 70.
Scientists continue to develop tests that help find specific types of cancer before signs or symptoms appear. This is called screening. The main goals of cancer screening are to:
- Reduce the number of people who die from the disease, or eliminate deaths from cancer altogether
- Reduce the number of people who develop the disease
Types of screening Test
Each type of cancer has its own screening tests. Some types of cancer currently do not have an effective screening method.
Breast self examination: During this exam, a woman looks and feels for changes in her own breasts. If she notices any changes, she should see a doctor.
Clinical breast examination: A medical professional looks and feels for any changes in the breast’s size or shape. The examiner also looks for changes in the skin of the breasts and nipples.
Mammography: Mammography is a type of x-ray specifically designed to view the breast. The images produced by mammography, called mammograms, can show tumors or irregularities in the breast.
Magnetic resonance imaging (MRI): MRI is not regularly used to screen for breast cancer. However, it may be helpful for women with a higher risk of breast cancer, those with dense breasts, or when a lump is found during a breast examination.
VIA: This test is direct visualization of cervix after application 5% acetic acid to the cervix. It identifies any precancerous lesion if present.
VILI: This test is similar to VIA, but in this test Lugol’s iodine is used instead of 5% acetic acid.
Pap test: Cells are scraped from the outside of a woman’s cervix. A pathologist then identifies any precancerous or cancerous cells. This test may be combined with HPV testing.
HPV test: This test also uses cells from the outside of a woman’s cervix. These cells are tested for specific strains of HPV. This test may be done alone or combined with a Pap test. An HPV test may also be done on a sample of cells from a woman’s vagina that she can collect herself.
Fecal occult blood test (FOBT): This test finds blood in the feces, or stool, which can be a sign of polyps or cancer. There are two types FOBT: Guaiac and immunochemical.
Colonoscopy: During this procedure, the doctor inserts a flexible, lighted tube called a colonoscope into the rectum. The doctor is able to check the entire colon for polyps or cancer.
Sigmoidoscopy: The doctor uses a flexible, lighted tube called a sigmoidoscope to check the lower colon for polyps and cancer. The doctor cannot check the upper part of the colon with this test.
Double contrast barium enema: This is an x-ray examination of the colon and rectum. The barium enema helps the outline of the colon and rectum stand out on the x-rays. Doctors use this test to screen people who cannot have a colonoscopy.
Stool DNA tests: This test analyzes DNA from a person’s stool sample to look for cancer. It uses DNA changes found in polyps and cancers to help a doctor decide whether a colonoscopy is needed.
Digital rectal examination (DRE): A DRE is a test in which the doctor inserts a gloved lubricated finger into a man’s rectum and feels the surface of the prostate for any irregularities.
Prostate-specific antigen (PSA) test: When screening for prostate cancer, the PSA test may detect small cancers that would never become life-threatening, but once detected will lead to treatment.
Screening studies for lung cancer have only been done in high risk populations, such as smokers and workers with occupational exposure to certain substances.
Low-dose helical or spiral computed tomography (CT) scan: A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors.
Complete skin examination: A doctor checks the skin for signs of skin cancer.
Skin self-examination: People examine their entire body in a mirror for signs of skin cancer. It often helps to have another person check the scalp and back of the neck.
Dermoscopy: A doctor uses a handheld device to evaluate the size, shape, and pigmentation patterns of skin lesions. Dermoscopy is usually used to for the early detection of melanoma