Breast cancer: early detection

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What is it about ?

Screening involves finding a condition or the risk of developing a condition in a person who has no symptoms. The goal of screening is to be able to identify and treat the condition at an early stage, before it reaches a stage that is more difficult or even impossible to treat. In other words, screening aims to find malignant conditions or lesions at a time when a cure is still possible.

There are 2 types of screening: opportunistic screening and systematic screening.

  • In the opportunistic screening, a condition is sought in patients who consult the doctor for other complaints. Thus, a doctor can, for example, offer breast cancer screening to women over the age of 50 who come to have their blood pressure checked.
  • In the systematic screening, a whole population group is invited to take a specific exam. All women between the ages of 50 and 69, for example, are encouraged to have a mammogram.

In Belgium, breast cancer screening is done systematically as part of a national screening program. All women aged 50 to 69 are therefore invited to have a mammogram every two years. As for women aged 70 to 74, they are only screened if they are in good physical condition. Finally, screening is considered in women aged 40 to 50 who are at moderately increased risk.

The ideal test is one which always gives a positive result in the presence of the disease and which always gives a negative result in the absence of the disease. Unfortunately, the ideal test does not exist. Sometimes false-positive and false-negative results are still possible. A false positive indicates that the person is sick when they are not, while a false negative indicates that the person is not sick when they are.

What test is used for screening for breast cancer?

The national breast cancer screening program calls for screening every two years. Women who are in the target group are encouraged to have a screening mammogram (a breast x-ray). During this examination, two ‘photos’ (x-rays) are taken: 1 from the side and 1 from top to bottom. The examination is carried out in approved mammography units, which are subject to strict quality controls. The participants in the program are divided into two groups: a group of women with an abnormal result, in whom additional tests must be performed, and a group of women without an abnormal result, who do not require additional tests.

Women who present with complaints or abnormalities on the screening mammogram are invited to undergo additional examinations in order to detect a possible lesion. This research can be done by means of an ultrasound or an MRI (magnetic resonance imaging).

What are the advantages and disadvantages of screening?

The advantage is obvious: In women who participate in the national screening program, breast cancer can be diagnosed at an early stage. The chances of recovery are indeed greater when a tumor is detected quickly. The risk of dying from breast cancer between the ages of 50 and 69 is reduced by at least 20%. And the decrease observed in women aged 69 to 74 is of the same order.

But there are also downsides:

  • A false positive can be a great source of stress and anxiety. While she does not have the disease, the woman receives a positive result and must undergo further examinations. Each year, 2 to 4% of tests give a positive result when the disease is not present.
  • Screening can also lead to overdiagnosis and overtreatment: for example, doctors may decide to treat a lesion that has never given rise to problems. Indeed, some tumors do not grow and never grow (we do not know which ones, unfortunately). This percentage is difficult to estimate, however, and lies somewhere between 3 and 30%.
  • The examination itself requires the use of rays, which in itself poses a risk of breast cancer. This risk depends on the age, frequency and duration of screening. It is estimated that out of 100,000 women who have a mammogram, 1 in 10 will develop breast cancer as a result of the exam. And the risk is even higher among women under the age of 40. The greatest caution is therefore called for.
  • The exam may be felt to be painful and uncomfortable.
  • A false-negative result can give a false sense of security. The woman is happy to learn that she has no problem, when in fact she has early breast cancer.

How common is breast cancer?

In Belgium, breast cancer is the first type of cancer in women. Belgium is one of the European countries with the most breast cancer among its residents. In 2016, the diagnosis was made in 10,735 women living in Belgium1.

What are the risk factors for breast cancer?

Fifteen (15) to 20% of breast cancers occur in women with a family history of breast cancer, without there being any question of a hereditary genetic predisposition. These cancers are probably due to a combination of genetic factors and environmental factors.

Studies have found a link between certain lifestyle factors and breast cancer risk. There is therefore a possible link between a diet high in saturated fat, excessive alcohol consumption, a lack of physical activity and weight gain following menopause and an increased risk of breast cancer. However, these risk factors do not justify carrying out screening tests outside the national screening program.

It could be chance that you have many breast cancers in your family. It can be the consequence of common risk factors. According to scientific studies, hereditary predisposition only occurs in 5 to 10% of cases. These are known mutations, such as mutations in the BRCA1, BRCA2, etc. genes. These mutations affect 1 in 1,000 people. The risk that a woman under the age of 70 who carries a mutation in the BRCA1 gene will actually develop breast cancer is estimated at 60-80%. The risk is somewhat lower in carriers of a BRCA2 gene mutation.

The risk of breast cancer is very complex and depends on many factors. It can also vary from person to person. An example: the probability that a 20-year-old woman will develop breast cancer before the age of 80 is 7.8% in the absence of breast cancer among her first-degree relatives. The risk climbs to 13.3% if one first degree relative develops the disease, and to 21.1% if two first degree relatives have the disease. The risk also increases when the parent in question develops the disease at a young age.

In what situations are genetic tests prescribed?

If there are breast complaints or concerns about breast cancer in the family, the doctor will ask which parents – on your mother’s side and on your father’s side – have had breast cancer. First-degree parents are the mother, father, brothers, sisters and children. Second-degree parents are grandparents, grandchildren, uncles, aunts, nieces, nephews, cousins, cousins, half-brothers and half-sisters. Third degree parents are great-grandparents, great-grandchildren, grand-cousins, grand-cousins, great-uncles and great-aunts, but they are not included in the breast cancer risk assessment.

Referral to a specialist is not necessary if the personal history does not indicate a significant risk and if there is only one case of breast cancer to report in a first or second degree relative. from 40 years old. However, it may be necessary to be referred to a specialist when certain criteria are met. Ask the general practitioner for advice.

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