Frequently Asked Questions: Cancer Screening Tests
General Questions
Q. What is the purpose of cancer screening?
A. Cancer screening is a medical attempt to find cancer or the changes that may lead to cancer at the earliest possible point, before symptoms develop, in order to remove or treat these abnormal cells before they can cause illness or perhaps shorten a person's life. A screening test does not itself treat cancer but can start the process by which cancers are diagnosed and treated.
Q. What makes a good screening test?
A. An effective cancer screening test is one that has been validated in well-conducted studies and shown to help lower the likelihood of a tested person dying from cancer. Screening tests are most effective when a certain type of cancer is common within a particular community or within a group that is at particularly high risk of developing that cancer.
Q. Is there such a thing as a bad screening test?
A. Yes. A test that might find cancer but produces no noticeable benefit to the persons screened (for example, using regular chest x-rays in an attempt to find lung cancer; this approach has been evaluated and found to be of no value) is a poor choice.
Q. How are cancer screening guidelines produced?
A. Panels of health care experts examine the published results of clinical investigations and determine whether a particular test is beneficial or not helpful; recommendations are made by consensus. In some instances, there may as yet not be enough information to decide if a test is useful. Guidelines are meant to assist making good decisions about health care but they are not ironclad rules.
Q. Why are there disagreements among experts about cancer screening?
A. Sometimes the information conflicts; different panels may interpret the information differently. Sometimes new information comes to light that changes a previous recommendation. It is often difficult to make recommendations that will fit every case.
Breast Cancer
Q. What is the difference between a mammogram and a 3D mammogram?
A. A conventional mammogram is similar to a standard x-ray; it looks at the breast tissue as a flat object. A 3D mammogram is more like a CT scan of the breast; it allows for an appreciation of the depth of the breast tissue and can be better at detecting subtle changes.
Q. What is breast awareness?
A. Familiarity with the specifics of one's own body and its changes. The idea is that this should make it easier to identify a potentially abnormal change early. However, there is no proof that breast self-examination helps to reduce the likelihood of dying from breast cancer; it does lead to a higher number of breast biopsies and helps find non-cancerous breast changes.
Cervical Cancer
Q. I know about Pap smears, but what is an HPV test?
A. HPV stands for human papillomavirus, which is now known to have a direct link to cervical cancer. The test detects the virus's genetic code, a very sensitive means of finding the virus in the tissues. The availability of this test means women may now be tested less frequently than in the past without jeopardizing their health.
Colorectal Cancer
Q. Can a virtual colonoscopy replace the standard colonoscopy test?
A. Virtual colonoscopy is a type of specialized radiology test using CT machines that is being investigated for its ability to find colon cancer and pre-cancerous changes in the colon. There is as yet no proof that this test is a good substitute for standard colonoscopy.
Lung Cancer
Q. I have never smoked, but I am regularly exposed to second-hand smoke. Should I be screened for lung cancer?
A. Current screening guidelines apply only to active smokers or those who have quit smoking within the past 15 years. There is no information now available that has shown a benefit to screening nonsmoking persons exposed to second-hand smoke.
Prostate Cancer
Q. I am confused about the guideline for prostate cancer. What happened to the PSA test?
A. The accumulated experience from several very large clinical investigations has raised considerable doubt as to the benefit of screening all men of a certain age for prostate cancer. As much as 40% of prostate cancers found through screening may never cause health problems for the affected persons because they are very slow-growing and unlikely to spread. But treatment for prostate cancer can be quite injurious and produce many adverse effects on a man's quality of life, possibly even leading to an earlier death from some other cause such as heart disease. The best current advice regarding testing for prostate cancer is to have a careful discussion of the risks and benefits with your personal health care provider who is best able to apply this information to your particular circumstance.
Skin Cancer
Q. What are the risk factors for skin cancer?
A. Cumulative exposure to ultraviolet radiation is the major risk factor associated with skin cancers that are not melanoma. The risk factors for melanoma are somewhat more varied; again, sun exposure (especially a history of severe sunburns sustained in childhood and teenage years), the use of tanning beds, and having certain types of moles all contribute. You should discuss your circumstances with your health care provider to determine whether and how often a thorough skin examination should be done.
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