What is screening for cancer?

Quick Answer
Tests or procedures that can detect the presence of a specific cancer in persons who is not experiencing any symptoms.
Expert Answers
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Cancers diagnosed: The most common cancer screenings detect breast, cervical, colorectal, and prostate cancer. Some require a blood test, while others require more extensive screening procedures.

Why performed: The purpose of screening tests is to allow early identification of cancer and prevent the progression of any existing cancer. Screening and early detection can save human lives, minimize the trauma of cancer illness, and conserve limited health care resources spent on costly cancer therapies.

People participate in screenings for various reasons. Sometimes they see screening as a preventive measure, and sometimes they undergo screening because they are at high risk for a cancer. Often health-conscious people participate in routine cancer screenings, and their health insurance pays the bill. Medicare (health insurance for older adults and the disabled) Part B covers certain key preventive cancer screening tests such as colorectal screening, mammograms, Pap smears and pelvic examinations, and prostate cancer screenings within certain parameters.

Screening for cancer offers many advantages for the public. Screening can save the life of someone who may have died without early intervention. When cancer is discovered, treatment can be started immediately and decrease the possibility of radical surgery or therapy. Early intervention also results in lower health care costs. A primary advantage is that the person who receives negative (benign) results has peace of mind that, at that point in time, cancer is not present. This is reassuring for anyone but especially for someone with a family history of cancer or who has other high risks for cancer.

However, the disadvantage of screening is that some false negatives may occur so the person does not believe there is a problem even when symptoms surface. Conversely, “false positives” can cause undue anxiety until further tests confirm there is no cancer. Sometimes the screening finds a cancer that is not treatable or is so advanced that the screening does not alter the negative outcome for the person. Another disadvantage is that borderline reports from cancer screenings can result in excessive testing and associated costs.

Breast self-exam (BSE): Breast cancer can be detected through several screening tests. One is palpation of the breast tissue through a monthly breast self-examination (BSE). Palpation is a noninvasive way to examine and screen for abnormalities in the breast such as cysts, lumps, or thickening. The patient can be taught to do an examination of her breasts each month and note visual or palpable changes in the breasts.

Patient preparation. The patient should stand unclothed from the waist up and view her breasts in a mirror. The best time to complete an examination is a few days after the completion of the menses, when swelling and tenderness are lessened.

Steps of the procedure. A breast self-examination is a five-step process:

  • The woman observes her breasts in the mirror, with her hands on her hips, for any visual changes in color, shape, and size. She looks for dimpling, swelling, or puckering of the skin as well as changes in the nipples or redness or rash on the breast.
  • She raises her arms over her head and observes the same as above.
  • She gently squeezes the nipples and observes for any liquid or discharge. (None should be present unless the woman is breast-feeding.)
  • She lies down and examines each breast with the opposite hand in a circular pattern, starting at the nipple and working outward. She palpates all breast tissue from the collarbone to the abdomen and from the armpit to the cleavage area.
  • She palpates the breast again in a sitting or standing position in the same pattern. Some women find that the examination is best completed when the skin is wet and slippery, such as in the shower.

After the procedure. The woman should record any observation and the date of each examination in a journal to be sure that it is completed monthly, preferably after the menses. This simple screening can detect early changes in the woman’s breasts.

Risks. None.

Results. The woman makes an appointment with her health care provider if abnormalities are noted. She should schedule her annual examination with the health care provider, which includes a clinical breast exam (CBE).

Mammograms: A screening mammogram uses x-rays to detect breast cancer. Mammography offers a noninvasive way to screen the breasts for cancer. A screening mammogram is useful when a woman has no history of problems with her breasts. Two x-ray views are taken of each breast. Scheduling the mammogram a week after the menses can decrease the patient’s discomfort, as hormonal soreness or tenderness is less at that time. An annual screening mammogram is recommended primarily for women over the age of forty. A screening mammogram can detect suspicious areas that may be breast cancer long before a mass can be palpated.

Patient preparation. The patient should avoid use of powders, deodorant, or lotion before the mammogram, since particles from these products can be viewed as abnormalities on the x-ray. The patient completes paperwork such as her history, last menses, risk factors, childbearing, surgeries, implants, birth control, hormone therapy, or any problems. The patient undresses from the waist up and wears an examination gown into the x-ray room. The patient can expect the x-rays to take about a half hour.

Steps of the procedure. The patient stands in front of the x-ray machine. A radiology technician exposes one breast at a time and places it on a film holder; the breast is compressed for a few seconds between the holder and a plastic paddle to take the x-ray. Good compression is necessary for accurate x-rays. Next the patient moves her side toward the machine, and the breast is compressed from the side. The x-ray is repeated.

After the procedure. A radiologist reads the x-ray either immediately or at a later time, depending on the facility’s availability to the radiologist.

Risks. The risk of radiation exposure through a screening mammogram is considered minimal. Most authorities agree that the benefit of screening for breast cancer outweighs the risk of low-dose radiation.

Results. Screening mammograms do not detect breast cancer 100 percent accurately. A normal result means that the mammogram detects no abnormalities, though a cancer can be hidden in dense breast tissue. Screening mammograms may be read as borderline, which may suggest that further testing (such as a diagnostic mammogram, ultrasound, or biopsy) is indicated to confirm the diagnosis of breast cancer.

Pap smear: The Pap smear is a screening test to detect changes in the cervix that may lead to cervical cancer in women. Early detection can increase the chance of successful treatment. All women need this screening examination, including sexually active women over the age of eighteen and those at risk for cervical cancer, such as women who had a previous abnormal pap smear. This test is usually performed during the woman’s annual gynecological exam.

Patient preparation. The woman should avoid douching or using any vaginal medications within forty-eight hours of the test. For accurate results, she should avoid intercourse within twenty-four hours of the screening. Optimal time for a Pap smear is at midcycle of the menses; a Pap smear cannot be performed during the menses. The woman should empty her bladder before the test to decrease discomfort.

Steps of the procedure. The Pap smear does not take long to perform. The patient lies on her back with her knees bent and her feet slightly apart. The health care provider will lubricate a speculum (an instrument that holds the walls of the vagina apart) and place it into the vagina. The patient will feel pressure as the provider swabs the cervix for a sample to examine. The sample is swabbed on a glass slide and sprayed with preservative. The slide is sent to the lab for microscopic examination for abnormal cells.

After the procedure. There are usually no side effects of this test. The lab results will be sent to the patient.

Risks. One risk is a false positive, which would lead to further testing, or a false negative, which might cause the person to ignore other warning signs of cervical cancer.

Results. Results are categorized as negative if no abnormal cells are seen. The patient usually receives a written notification of the results. Patients need to seek further testing from their health care provider for abnormalities.

Fecal occult blood, sigmoidoscopy, colonscopy: Colon cancer is the third leading cause of cancer death in the United States. The first screening test for colon cancer is the fecal occult blood sample. This test detects blood in the stool. The next screening is a sigmoidoscopy or colonoscopy. Regular rectal and colon screening is advised in persons over fifty years of age and in those at high risk. This includes a fecal test annually, a sigmoidoscopy every five years, and a colonoscopy every ten years after age fifty-five.

Patient preparation. Certain medications (aspirin and aspirin products, ibuprofen products, iron tablets, and vitamin supplements) should be avoided for a week before screening. Prescribed medications can usually be taken, but the physician should be consulted. A sigmoidoscopy or colonoscopy requires preparation of the bowel. The exact preparation used may vary by provider preference, but these preparations usually include a diet of clear liquids for twenty-four hours prior to the test as well as a liquid laxative about two to four hours before the examination.

Steps of the procedure. Both a sigmoidoscopy and colonoscopy require the insertion of a rigid or flexible tube that contains a lens and a light into the colon. The provider can visualize the rectum, lower colon (or sigmoid colon), or upper colon.

After the procedure. Patients may need someone to drive them home after this test, especially if they have sedation. The patient can experience some soreness and mild cramping due to the air that was injected into the colon for the test, but this condition improves as the air is passed. No other aftercare is required.

Risks. A slight risk of bleeding is possible, especially when the patient has decreased clotting capacity. A perforated (torn) colon is a serious but rare complication following a sigmoidoscopy or colonoscopy.

Results. A normal result is one where the colon walls are smooth and without polyps, inflammation, or tumors. An abnormal result would be present when the colon shows precancerous polyps or tumors. A biopsy and surgical removal of the polyps or tumors would be scheduled.

Digital rectal exam (DRE) and prostate-specific antigen (PSA) blood test: Prostate cancer is the second leading cause of death in men. By the age of fifty, men should have screening tests for prostate cancer; in high-risk men, screening should start at the age of forty-five. The main screening tests for prostate cancer are digital rectal exam (DRE) and the prostate-specific antigen (PSA) blood test. The prostate is the male reproductive organ located under the bladder and in front of the rectum.

Patient preparation. No special preparation is required.

Steps of the procedure. For the digital rectal exam, the patient is dressed in an examination gown and placed in a relaxed position (such as lying on his side or resting over an exam table) with the rectum accessible. The doctor inserts a well-lubricated, gloved finger into the rectum and feels the size of the prostate.

After the procedure. No residual patient discomfort occurs.

Risks. None.

Results. If abnormal results are reported from either the digital rectal exam or prostate-specific antigen test, the patient will need further testing to confirm a cancer diagnosis.


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Miller, Anthony B., ed. Advances in Cancer Screening. Boston: Kluwer, 1996. Print.

Querna, Elizabeth. “Breast Cancer Screening: What Is the Best Way to Find Out If You Have the Disease?” US News & World Report 9 Sept. 2004. Print.

Scholefield, John, and Cathy Eng. Colorectal Cancer: Diagnosis and Clinical Management. Hoboken: Wiley, 2014. Print.