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 tests
Each type of cancer has its own screening tests. Some types of cancer currently do not have an effective screening method. Developing new cancer screening tests is an area of active research.
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.
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.
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.
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.
Human papillomavirus (HPV) testing. Cells are scraped from the outside of a woman’s cervix. These cells are tested for specific strains of HPV. Some strains of HPV are more strongly linked to an increased risk of cervical cancer. This test may be done alone or combined with a Pap test (below). An HPV test may also be done on a sample of cells from a woman’s vagina that she can collect herself.
Pap test. This test also uses cells 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.
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.
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.
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.
Head and neck cancers
General health screening examination. The doctor looks in the nose, mouth, and throat for abnormalities and feels for lumps in the neck. Regular dental check-ups are also important to screen for head and neck cancers.
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.
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. This blood test measures the level of a substance called PSA. PSA is usually found at higher-than-normal levels in men with prostate cancer. However, a high PSA level may also indicate conditions that are not cancerous.
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.
Risks of screening
Screening tests can help doctors find a cancer at an earlier, more treatable stage. This may help improve survival. However, cancer screening also has a number of risks. These risks include:
Overdiagnosis. Screening tests may find slow-growing cancers that would not have caused any harm during a person's lifetime. As a result, some people may receive potentially harmful, painful, stressful, and/or expensive treatments that they did not need.
False positives. Sometimes a screening test will suggest that a person has cancer when they do not.
Increased testing. Doctors may run additional tests that a person may not need because of overdiagnosis and false positives. These tests can be physically invasive, costly, and cause unnecessary stress and worry.
False reassurance. Sometimes a screening test will suggest a person does not have cancer when they actually do. As a result, a person may not get the treatment he or she needs.