For some cancers, tests have been developed that can be done regularly to check specifically for the presence of that individual cancer. These tests are called screening tests because they have the ability to identify someone who has the early signs of a particular cancer even though they may not yet have experienced any notable symptoms.

If these specific signs are detected, then the test is referred to as positive. However, a positive test does not necessarily mean that the person has a cancer  in general, other tests are needed to make a complete diagnosis.

A screening test can identify cancer at an early stage, when it can be most effectively treated. As such, it is an invaluable tool in reducing the time before detection and hence the risk of discovering an advanced cancer that may not be so easily treated.

Some screening tests can even prevent cancer from developing at all. Some cancers such as cancer of the cervix (neck of the womb) are preceded by small changes that act as early warning signs. If these are detected early enough it may be possible to prevent the cancer from developing at all.

Screening tests are only available for those cancers where a reliable way of detecting the cancer or pre-cancer has been developed by scientists. It is also important for there to be an effective treatment available for any possible cancers found if the test is to produce real benefit to the quality of life of the patient and their community.

Cancer markers are available for other variations such as bowel and ovarian cancer, but are mostly used to monitor progress after treatment / surgery.

There is evidence that screening people over 50 for non-visible (occult) blood in the stool could reduce mortality from bowel cancer.

Whilst such tests would be easy to administer, there are doubts as to how reliable they would be. Not all cancers bleed, meaning that a negative result may still mean a person is at risk.  A colonoscopy may be necessary to detect bowel cancer.

Breast cancer screening

Of the 35,000 newly diagnosed cases of breast cancer each year, most of them are in the over-55 age group.

Breast screening is performed using mammography and is vitally important in the early detection of small changes that could indicate a cancer too small to be felt by the woman or her doctor.

If you are a woman aged between 50-64, you will be invited by your GP for screening at 3-yearly intervals. Studies show that the number of deaths from breast cancer in this age group can be reduced by 40% in those who attend regular mammogram screenings.

It is possible that regular screening may be extended to the age of 70 by 2004; currently if you are over 64 you will not automatically be called. If this applies to you, remember that you can always request a mammogram and are encouraged to do so.  The risk of cancer is no less in this older age group.

What is a mammogram?

A mammogram is a type of x-ray. Its aim is to detect abnormalities in breast tissue before they have had a chance to grow and spread.

Does it hurt?

Having a mammogram does not hurt. What happens is that each breast is carefully manoeuvred onto a breast-plate on the x-ray machine and then firmly but gently compressed using a clear glass/perspex plate in order for an x-ray to be taken. Two images are generally taken on the first appointment; one or two on subsequent visits.

The compression of the breast against the breast-plate may be uncomfortable  but be reassured that the procedure only lasts a short time. Studies have shown that most women rate the experience as comparable with having their blood pressure taken.

Is it dangerous?

There is an extremely small risk of inducing breast cancer by radiation exposure from mammography. A very limited amount of radiation in used.  Current estimates claim that for every 2 million women aged over 50 who have been screened, the radiation from mammography will cause no more than one extra cancer every 10 years.

What happens next?

If your mammogram detects an abnormal area in your breast, you will be referred for further tests. Although mammograms are very sensitive, they cannot detect whether an abnormal area is a cancer. Additional investigation is necessary to make a definite diagnosis one way or the other.

Sometimes an ultrasound scan is used to distinguish whether an identified lump is full of fluid (a cyst) or solid (possibly a tumour). Alternatively fine needle aspiration cytology  might be used. Here a needle is inserted into the lump, sometimes guided by ultrasound imaging if the lump is too small to feel (palpate). This method also allows a sample of cells to be removed and these can then be studied under a microscope to accurately determine whether the lump is benign or malignant.

Does having HRT affect breast screening?

There has been some suggestion that women on HRT have denser breast tissue  similar to that found in younger women. It has been implied that this denser, more compact breast tissue may make detecting abnormalities more difficult.  In general, after the menopause, the breast becomes increasingly made up of fat, which produces a clearer and more reliable mammogram. This is something to be aware of, but more frequent mammograms are not suggested in this instance.

Again, examining your own breast is vitally important. More than 90% of breast cancers are found by women themselves.

Cervical cancer screening

Cervical screening is performed using cervical smear tests. All women between 20- 64 are eligible for this test. If you are registered with a GP, you will be invited by your local health authority for screening at 3-5 yearly intervals. You can choose whether to have the test done at your GP practice or a family planning clinic. Most people tend to choose their local GP practice. The test can be done by your doctor or, more likely, the practice nurse.

What is a cervical smear?

A cervical smear is a test where a sample of cells from the cervix (the neck of the womb) is removed and examined using a microscope for the presence of abnormal cells. These are not cancer  but left undetected have the potential to develop into cancer. Early detection makes sure that this does not happen.

Does it hurt?

The person performing the smear test uses an instrument called a speculum to gently open up the vagina and then uses a spatula to sweep around the surface of the cervix to take a sample of cells. This procedure can be uncomfortable, particularly if you are not relaxed.

What happens next?

The sample of cells is then transferred or smeared onto a slide. The slide is sent to the laboratory for examination. How the cells look under the microscope will determine what happens next.

The vast majority of cervical smear tests display normal cells.  Women will be recalled routinely in 3-5 years for their regular cervical smear test.

Some smear tests will identify abnormal cells. This does not mean you have cancer. It means that abnormal cells have been identified, which if left untreated could lead to a cancer. The degree of change or abnormality detected will dictate what happens next in this situation.

Not everyone who has abnormal cells identified will need treatment. If the cells are borderline abnormal all that may be required is a repeat smear in 6-12 months. If the cell changes observed are greater, further investigation may be suggested, such as a colposcopy.

A small proportion of women may be asked to return for a second smear purely because the first was inadequate. In these cases, the cells on the slide cannot be assessed properly either because they have been smeared too thick or too thin or possibly due to the presence of blood on the slide. Another smear test is necessary in order to gain an accurate result.

What is a colposcopy?

A colposcope is a low-powered-light microscope that is used to examine the surface of the cervix in more detail in order to gain a more accurate picture of the extent and severity of the problem and then to determine appropriate treatment.  This procedure is performed by specially trained clinicians at an outpatient clinic.

03/06/2009