Cancer screening

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Cancer screening is the act of looking for cancer before a person has any of the symptoms of the disease. Usually, when cancers are found earlier, they are easier to treat. Physicians and scientists are always looking for ways to find and treat diseases earlier and to better understand why some people get cancer and some don’t.

If a screening test is abnormal, then further testing can be done. Not all abnormal screening tests mean you have a particular cancer. That is why you will be sent for diagnostic testing. Diagnostic tests are more specific to the particular cancer.

For the average-risk adult, there are four common screening tests. Pap smears are used to screen for cervical cancer. Mammograms are used for breast cancer. Prostate specific antigen is used for prostate cancer, and a colonoscopy or sigmoidoscopy is used for colon cancer. To date, there are no good screening tests for lung cancer or ovarian cancer.

Cervical cancer
When to begin pap smears is a topic of frequent debate. Although it is generally accepted that there is little value in screening women who are not sexually active, many physicians will begin screening most women between the ages of 18 and 21. Screening may always begin sooner if a woman is sexually active and should always be done in conjunction with the use of birth control and hormone therapy.

The pap smear targets the transformation zone of the cervix where the majority of cervical cancers arise. There is no reason to do pap smears on women who have had complete hysterectomies unless the reason for the hysterectomy is not known, or there are other risk factors present. Women who still have their ovaries will still need a routine pelvic exam.

Pap smears should be done yearly until age 30. Some physicians are comfortable lengthening the screening interval at age 30, especially if they have an established relationship with the woman and she has had three prior normal screenings. Some reasons not to lengthen the interval would be a history of cervical cancer, infection with HPV (human papilloma virus) or other sexually transmitted diseases or high-risk sexual behaviors.

When to discontinue pap smears is also not clear. The risk of cervical cancer declines with age. Screening in older women is important if they have never been screened. Most screening can be stopped by age 70.

Breast cancer
In the United States, more women get breast cancer than any other kind of cancer except skin cancer. Only lung cancer kills more American women. Fortunately, the death rates for breast cancer are coming down. Men also get breast cancer, but those numbers are small.

Mammography is the main screening tool for breast cancer and should be done routinely for women ages 40 to 70. Mammography uses ionizing radiation to image breast tissue. This screening tool can identify breast cancers too small to be felt on a physical exam and may also lead to the discovery of more breast cancers in situ, which is a noninvasive form of the disease.

Another good screening tool is a clinical breast exam done yearly by a physician. Used together, mammography and clinical breast exams have shown to reduce breast cancer mortality. How often to have a mammogram is the subject of much debate, and the practices around the world vary greatly. The United States Preventative Services Task Force (USPSTF) recommends screening mammography, with or without a clinical breast exam, every 12-33 months.

When to stop mammography is uncertain. Women who develop breast cancer at an older age face a higher probability of dying from it but also have a greater chance of dying from other causes.

Self-breast exams are also touted to be a good screening tool, but, actually, this may not be the case. Some research suggests that self-breast exams lead to many unnecessary breast biopsies and to the diagnosis of benign breast lesions.

Other tests that may be performed on the breasts include ultrasound, using sound waves to exam lesions and MRI. MRI is becoming a more important tool because it seems to be a better screen for women who have a genetic tendency toward breast cancer. In Arizona this has become a very important topic. Recent research suggests that Hispanic women are more likely than white or black women to have hereditary forms of breast cancer.

Prostate cancer
Prostate cancer is the most common cancer in men in the United States and the second-leading cause of cancer deaths.

Older men, African-American men and men with a family history of prostate cancer are at an increased risk for developing and dying from prostate cancer. The PSA test (prostate specific antigen) is a blood test routinely done as a screen for prostate cancer. It is more sensitive than a digital rectal exam for detecting prostate cancer. Unfortunately, there is some evidence that treatment for prostate cancer detected by screening does not improve health outcomes in men younger than 75 and may even do harm. The screening process itself produces at least small harms such as pain and discomfort associated with prostate biopsies.

Treatment for prostate cancer may cause erectile dysfunction, urinary incontinence, bowel dysfunction and death. Many of the men who find out they have prostate cancer from a screening test may never have developed any of the symptoms related to the cancer in their lifetime.

Your doctor should be able to discuss with you if these screenings are best for you. Even if you do determine that this screening is best for you, the optimal ages are 50 to 74 years of age. Men younger than 75 who have other chronic medical problems and have a general life expectancy of less than 10 years are not likely to benefit from screening.

Colon cancer
Colorectal cancer is the third-most common type of cancer and the second-leading cause of cancer death in the United States. Unfortunately, screening for this cancer greatly lags behind screening for other types of cancer. It is estimated that 18,000 deaths a year could be prevented if adequate screening was done. The general recommendation is to begin screening at age 50. People who have first-degree relatives with a history of colorectal cancer may want to start screening earlier. More than 80 percent of diagnosed cases occur in patients over 55 years of age. There is an increased incidence with increasing age, male sex and African-American race.

The three primary screening tools for colorectal cancer are fecal occult blood testing, sigmoidoscopy and colonscopy to detect early-stage cancer and pre-cancerous polyps.

Colonoscopy is considered to be the preferred test, and, if either of the other two screens are positive, then a colonoscopy is required regardless. The biggest concern regarding colonoscopy is the risk of colon perforation, but this actually occurs only in about 3.8 cases for every 10,000 procedures performed.

Flexible sigmoidoscopies were once a common screening tool in many physicians’ offices. They are falling out of favor because of discomfort, and many physicians no longer choose to do these tests in their office and refer their patients to a specialist for a colonoscopy. Fecal occult blood testing is a simple test that can be done in the privacy of your own home.

The largest reduction in colorectal cancer comes from the detection and removal of early-stage cancers. Screening may continue up to age 75. It is generally not recommended in older adults due to the increased risk of the test itself, although every case must be evaluated individually.

New developments for screening are being reviewed all of the time. A very interesting research study is being done in California. Dogs are being studied to see if they can identify cancers in humans earlier. The theory is that cancers give off a specific odor that dogs can be trained to identify. They are already using dogs to alert their owners to impending seizure activity and low blood sugars.

So, the next time you go to give your dog a hug, remember he really may be your best friend.

Jean Paul, D.O., graduated from Des Moines University in 1997. Board certified in Family Practice, she has been working for Sun Life Family Health Center in Maricopa since 2000. Dr. Paul can be reached at (520) 568-2245.

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