Cancer Screening Test Facts*
*Cancer screening test facts medical author: Melissa Conrad Stöppler, MD
- Cancer screening tests are tests that look for the presence of cancer in healthy people or people without symptoms of cancer.
- Cancer screening tests are designed to find cancers at an early stage when they are more treatable.
- Some cancer screening tests have been found to lower the death rate (mortality rate) from certain cancers.
- Examples of some common cancer screening tests that are known to lower cancer death rates include colonoscopy for colon cancer, mammography for breast cancer, and Pap smear for cervical cancer.
- Some cancer screening tests are recommended only for people at high risk of developing cancer, such as MRI of the breast for women at increased risk of breast cancer.
Many cancer screening tests are in use. Some tests have been shown both to find cancer early and to lower the chance of dying from the disease. Others have been shown to find cancer early but have not been shown to reduce the risk of dying from cancer; however, they may still be offered to people, especially those who are known to be at increased risk of cancer.
Screening Tests That Have Been Shown to Reduce Cancer Deaths
- Colonoscopy, sigmoidoscopy, and high-sensitivity fecal occult blood tests (FOBTs)
These tests have all been shown to reduce deaths from colorectal cancer. Colonoscopy and sigmoidoscopy also help prevent colorectal cancer because they can detect abnormal colon growths (polyps) that can be removed before they develop into cancer. Expert groups generally recommend that people who are at average risk for colorectal cancer have screening at ages 50 through 75.
- Low-dose helical computed tomography
This test to screen for lung cancer has been shown to reduce lung cancer deaths among heavy smokers ages 55 to 74.
This method to screen for breast cancer has been shown to reduce mortality from the disease among women ages 40 to 74, especially those age 50 or older.
- Pap test and human papillomavirus (HPV) testing
These tests reduce the incidence of cervical cancer because they allow abnormal cells to be identified and treated before they become cancer. They also reduce deaths from cervical cancer. Testing is generally recommended to begin at age 21 and to end at age 65, as long as recent results have been normal.
Breast Cancer Screening
A mammogram is an X-ray test that produces an image of breast tissue on film. This technique, called mammography, is used to visualize normal and abnormal structures within the breasts. Mammography, therefore, can help in identifying cysts, calcifications, and tumors within the breast. It is currently the most efficient screening method to detect early breast cancer. Physical examinations typically find breast cancers when they are much larger than those detected by mammography.
Mammography can be used to discover a small cancer in a curable stage; however, it is not foolproof.
Other Screening Tests
- Alpha-fetoprotein blood test
This test is sometimes used, along with ultrasound of the liver, to try to detect liver cancer early in people at high risk of the disease.
- Breast MRI
This imaging test is often used for women who carry a harmful mutation in the BRCA1 gene or the BRCA2 gene; such women have a high risk of breast cancer, as well as increased risk for other cancers.
- CA-125 test
This blood test, which is often done together with a transvaginal ultrasound, may be used to try to detect ovarian cancer early, especially in women with an increased risk of the disease. Although this test can help in diagnosing ovarian cancer in women who have symptoms and can be used to evaluate the recurrence of cancer in women previously diagnosed with the disease, it has not been shown to be an effective ovarian cancer screening test.
- Clinical breast exams and regular breast self-exams
Routine examination of the breasts by health care providers or by women themselves has not been shown to reduce deaths from breast cancer. However, if a woman or her health care provider notices a lump or other unusual change in the breast, it is important to get it checked out.
- PSA test
This blood test, which is often done along with a digital rectal exam, is able to detect prostate cancer at an early stage. However, expert groups no longer recommend routine PSA testing for most men because studies have shown that it has little or no effect on prostate cancer deaths and leads to overdiagnosis and overtreatment.
- Skin exams
Doctors often recommend that people who are at risk for skin cancer examine their skin regularly or have a health care provider do so. Such exams have not been shown to decrease the risk of dying from skin cancer, and they may lead to overtreatment. However, people should be aware of changes in their skin, such as a new mole or a change to an existing mole, and report these to their doctor promptly.
- Transvaginal ultrasound
This imaging test, which can create pictures of a woman's ovaries and uterus, is sometimes used in women who are at increased risk of ovarian cancer (because they carry a harmful BRCA1 or BRCA2 mutation) or of endometrial cancer (because they have a condition called Lynch syndrome). But it has not been shown to reduce deaths from either cancer.
- Virtual colonoscopy
This test allows the colon and rectum to be examined from outside the body. However, it has not been shown to reduce deaths from colorectal cancer.