Mammogram: A screening tool to detect breast cancer

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THE DOCTOR SAYS
By Dr MILTON LUM

According to the World Health Organisation’s International Agency for Research on Cancer, regular mammogram screening could reduce deaths from breast cancer by 35%.

BREAST cancer is the most common cancer in women in most parts of the world. There is a geographical variation, with the highest incidence in North America and North Europe, an intermediate incidence in South America and South Europe, and a lower incidence in Asia and Africa.

According to the Malaysian Second Report of the National Cancer Registry, there were 3,738 cases in 2003. It was the commonest cancer in all ethnic and age groups of Malaysian women, comprising 31.0% of all cases reported.

The peak incidence was in the 50 to 59 years age group, with a decline in older age groups. About 64.1% of all cases were diagnosed in women aged between 40 and 60 years.

Seeing lumps: A mammogram is an X-ray of the breasts. It can be used to detect breast cancer in women who have no signs or symptoms, in which case it is called a screening mammogram.

Many women regard the breast as a badge of their femininity, and they can be markedly affected psychologically if they have breast cancer. Experience worldwide has shown that its early detection and treatment helps in making possible a high cure rate.

Mammograms play an important role in the screening and diagnosis of breast cancer and other breast conditions. According to the World Health Organisation’s (WHO) International Agency for Research on Cancer (IARC), regular screening could reduce deaths from breast cancer by 35%.

A mammogram is an X-ray of the breasts. It can be used to detect breast cancer in women who have no signs or symptoms, in which case it is called a screening mammogram. When it is used for diagnosis in women who have signs and symptoms of breast disease, e.g. a lump, pain, nipple discharge, or change in breast size or shape, it is called a diagnostic mammogram.

A screening mammogram usually entails the taking of two X-ray images of each breast to detect lumps that are not felt on touch. Small amounts of calcium (microcalcifications), which occasionally is indicative of breast cancer, can also be detected.

A diagnostic mammogram is used when there are signs or symptoms of breast disease. It is also used to evaluate images detected in a screening mammogram or when there is difficulty in doing a screening mammogram, e.g. presence of breast implants. It entails the taking of more X-rays to obtain images from various angles. Hence, more time is required than a screening mammogram.

The images obtained in a mammogram are stored on film or digitally. In the case of the latter, the images stored in a computer can be magnified, enhanced, or manipulated for detailed assessment, which is not possible with images stored on film.

This has the advantage of assessing subtle image differences, assessment at another site (teleradiology), and fewer repeat X-rays, leading to a decreased radiation exposure.

There is no difference in the procedure for conventional film or digital mammography.

Mammogram

The patient is asked to remove the top of her dress by a female radiographer. Each breast is placed firmly between two small plates of an X-ray device, one at a time. The compression of the breast facilitates the taking of clear X-ray images.

Some women find this uncomfortable, others find it painful. However, the discomfort is transient, i.e. only during the compression of the breast. There is evidence that discomfort or pain is reduced by quality information about the procedure and control over the breast compression.

Painkillers (analgesics) are not helpful.

Two X-rays are usually taken in a screening mammogram, one from above, and the other from the side. This process doubles the cancer detection rate.

The X-ray images are assessed by a specialist (radiologist). If the images are not clear, or abnormalities are found, the patient will be asked to return for additional X-rays.

The time taken for the report to be available depends on the healthcare facility. It is natural to have some degree of anxiety while waiting for the result of a mammogram, which will be reported by the radiologist.

One should remember that the anxiety is balanced by the benefits of screening, which detects breast cancer early, making it possible to have better cure rates, and sometimes, less radical treatment.

It is essential to inform the radiologist or radiographer if there is a possibility of pregnancy, and if there is a breast implant present. In the case of the former, the mammogram will be deferred to a later date. In the case of the latter, techniques may be used to obtain images of as much breast tissue as possible.

Screening in women at risk

Who is to have a mammogram is determined by the factors that increase a woman’s risk of breast cancer.

Age is the most significant risk factor. The older a woman is, the greater the risk. However, the risk is not the same for all women in a certain age group.

Women with the following risk factors are at increased risk:

> Personal history – Women who have had breast cancer are more likely to develop another breast cancer.

> Family history – The risk is increased in women whose mother, sister and/or daughter have breast cancer, particularly if it occurred before 50 years of age. It is also increased if a male relative has breast cancer.

> Genetic history – Women who have the BRCA1 and BRCA2 genes are at increased risk. Those who have certain changes in these genes have more risk than those without the changes.

> Menstrual history – Women whose first menstrual period occurred before 12 years of age, or whose menopause occurred after 55 years of age, are at increased risk.

> Reproductive history – Women who delivered a baby after 30 years of age or who never delivered a baby are at increased risk.

> Hormone therapy – Women who use combined oestrogen and progestogen hormone therapy for more than five years are at increased risk. Women who took diethylstilbestrol (DES) to prevent miscarriage may have a slightly increased risk. The effects of DES in the daughters of women who took it remain unclear.

> Radiation therapy – Women who had radiation therapy to the chest, including the breast, e.g. in Hodgkin’s lymphoma, before 30 years of age, are at increased risk.

> Body weight – The risk is increased in the overweight or obese.

> Physical activity – Physical inactivity throughout life may increase risk.

> Alcohol consumption increases risk; the greater the consumption, the greater the risk.

> Breast density – Women with dense breast tissue have a higher risk.

> Breast biopsy changes – The risk is increased in women with increased abnormal but non-cancerous cells (atypical hyperplasia), abnormal but non-invasive cells in the lobules (lobular carcinoma in situ), and in the ducts (ductal carcinoma in situ).

Women are advised to discuss with their doctor when screening should commence.

Benefits and risks of mammograms

There are benefits and risks for any procedure, and mammograms are no exception. Women are advised to discuss this with their doctors, as well as any anxiety they may have.

The benefits of screening, i.e. early detection and treatment, outweigh the small risk of radiation from the procedure. It has been estimated that there is a less than one in 25,000 chance of the radiation from a mammogram causing breast cancer. Most large scale breast cancer screening programmes report between five and 10 breast cancers detected for every 1,000 women screened, the majority of which are at an earlier, curable stage.

However, it is a fact that the detection of cancer does not necessarily mean that lives are saved. A rapidly growing breast cancer may have spread by the time it is detected by mammography. It is also a fact that mammography may not benefit a woman with other life threatening conditions.

There may be false negative results, i.e. the mammogram appears normal, when in fact, there is a cancer present.

In general, the false negative rate for a screening mammogram can be as high as 20%. The major cause of false negative results is increased breast density.

All breasts have dense and fatty tissue. This is found in the glands and connective tissue of the breast, and have a similar density to breast cancer in the mammograms, thereby making diagnosis more difficult in women with denser breasts. False negative results lead to delay in treatment and a false sense of security.

There may also be false positive results, i.e. the mammogram is diagnosed as abnormal, when in fact, there is no cancer present. This results in additional investigations, i.e. diagnostic mammograms, ultrasound and/or biopsy to determine if cancer is present. False positive results lead to anxiety, additional discomfort, increased expenditure, over-investigation, and overtreatment.

Breast ultrasound

Breast ultrasound complements mammograms. High frequency sound waves are used to produce images of breast abnormalities.

It is a useful procedure if the breast is dense or if the doctor wants to know whether a lump is solid or contains fluid. It also facilitates needle aspiration or biopsy of a suspected abnormal area.

Category: Milton's Corner
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