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What are the main risk factors?

Risk factor is any situation that increases the probability of occurrence of a disease or health problem. Women with risk factors for breast cancer will not necessarily get cancer, and the absence of risk factors does not eliminate the chance of having it. The more risk factors an individual has, the greater their chances of developing a particular disease.

About 70% of affected women with breast cancer do not have a clearly identifiable risk factor. However, when comparing women with risk factors and women without risk factors, the incidence of cancer is clearly higher in the first group.

Risk factors for breast cancer:

1- Female gender

Women are 100 times more likely to get breast cancer than men.

2- Age

The risk increases from the age of 40, reaching its peak around the age of 55-60. About 60% of women with breast cancer are over 50 years old.

While the risk of breast cancer in women in their 30s is only 1 in 2000, in women in their 75s the risk is 1 in 10. Look by age group.

– Up to 49 years of age: 1 case for every 51 women.

– Between 50 and 59 years: 1 case for every 43 women.

– Between 60 to 69 years: 1 case for every 23 women.

– Over 70 years of age: 1 case for every 15 women.

3- Ethnicity

Whites are the ethnic group with the highest incidence of breast cancer. Blacks have a slightly lower risk, however, their mortality is higher due to more aggressive tumors, and the fact that this population has less access to diagnostic means and early treatment. Hispanics and Asians have about 30% lower risk of breast cancer than whites. With the incorporation of Western habits in other countries (food, fast food, fewer children, obesity, pollution), there have been higher incidences in low- and middle-income countries.

4- Family history

Having a first-degree relative with breast cancer increases your risk of having it 1.8-fold. Having two first-degree relatives with breast cancer increases the risk 2.9-fold. If you have a first-degree relative diagnosed with breast cancer before age 40, then your risk of also having it before age 40 increases by 5.7 times.

However, despite these data, only 15% of women with breast cancer have a positive family history. The other 85% of cases occur in women without a family history.

Family history is also important in identifying some genetic mutations that favor the emergence of breast cancer. When several family members have the disease, we are probably dealing with a family that has germline mutations. Women with these altered genes have a 65% chance of getting breast cancer up to 70 years of age. The BRCA 1 and BRCA 2 genes are responsible for somewhere around 5% of breast cancer cases.

5- Personal history of breast cancer

Those who have had breast cancer once, are 4 times more likely to have a second breast cancer, whether in the same or contralateral breast.

6- Benign breast lesions

Most benign breast lesions do not carry an increased risk of breast cancer. Among them, we can mention simple fibroadenoma, cystic fibrosis, papilloma and ductal ectasia. However, some precursor lesions, such as atypical ductal hyperplasia and atypical lobular hyperplasia are recognized risk factors, increasing the risk of breast cancer by approximately 5 times.

7- Age at menarche (first menstruation) and menopause

Women with early menarche (before age 12) and/or late menopause (after age 55) are at increased risk of breast cancer

8- Thoracic radiation

People with a previous history of cancer who have undergone radiotherapy in the thoracic region, as in the treatment of lymphoma, people exposed to radiation such as atomic bomb survivors or people who have come into contact with radioactive material, such as in nuclear power plant accidents, are at higher risk of breast cancer. This risk is even greater if the exposure occurred during youth.

9- Breast Density

Breast density represents the ratio of glandular parenchyma to breast fat. The more gland, the denser. Dense breasts have a higher risk of breast cancer and a greater difficulty in diagnosing it by mammography.

10- Age at first birth and number of children

Women who have their first child early have a lower risk of breast cancer when compared to women who give birth after 30 years of age. Over 40 years, who have never had children, are at higher risk, about 30% higher than women with children. It is estimated that each child reduces the risk of breast cancer by 7%.

11- Breastfeeding

Breastfeeding reduces the risk of breast cancer. A 4.3% reduction is estimated for every 12 months of breastfeeding performed. Women with large offspring and long-term breastfeeding are better protected.

12- Hormonal contraceptives

The relationship between birth control pills and the incidence of breast cancer has lost strength in recent years with the decrease in the amount of hormones present in the drug. The risk was higher in those who used the contraceptive for more than ten years and were over 40. In addition to the pill, the intrauterine device (IUD) with progesterone was also linked to risks.  The threat linked to the aforementioned contraceptive methods is small, we have to assess whether the pill brings more risks than benefits.

13) Hormone Replacement Therapy (HRT)

Collaborative Group on Hormonal Factors in Breast Cancer analyzed the long-term effects of HRT, taking into account age at first use, duration of use and time since last use. In turn, it compared estrogen alone versus no use and combined therapy (estrogen and progesterone) versus no use.  The data showed that compared to non-users, women who started HRT soon after menopause had a significantly increased risk of invasive breast cancer. The relative risks were higher for combination therapy users versus non-users than for estrogen users alone. In former HRT users, the relative risks were lower than in current users, but the risks remained elevated for more than 10 years after discontinuing therapy.

14- Obesity

The larger the fat tissue, the greater the risk of breast cancer. Women with a body mass index (BMI) greater than 33 kg/m2 are 27% more at risk than women with a normal BMI. This risk is even greater in women after menopause.

In addition to chronic inflammation, experts highlight other biological processes that explain the relationship:

a- Dysregulation of cell death. After a while, the cells program themselves to die. The process is natural and known as cellular apoptosis. Studies show, however, that obesity can disrupt this process - which contributes to dysfunctional cells remaining in the body.

b- Obesity contributes to the secretion of pro-inflammatory substances. These substances promote the growth of cells with a more cancerous profile.

c- Increased blood vessels. Obesity favors the growth of blood vessels, in a process known as angiogenesis. Tumors end up using these new blood vessels for their nutrition.

d- Excessive abdominal fat. One of the factors that contribute to cancer is excess fat in the abdominal region. The fat in this region becomes an endocrine organ, capable of producing hormones and stimulating cell multiplication.

e- Change in the intestinal microbiota. Studies also show that obesity contributes to a change in the profile of the bacteria that make up the intestinal tract, a characteristic that also favors greater inflammation.

f- Greater insulin secretion. Insulin, a hormone that contributes to glucose being used by cells, is also involved in the inflammation process initiated by obesity.

g- Elevated levels of sex hormones. Obesity contributes to increased production of sex hormones and this is particularly important in increasing the production of estrogen, a female hormone.

15- Alcohol consumption

Alcohol consumption increases the risk of breast cancer. The greater the consumption, the greater the risk. A trend was shown between the increased risk of developing breast cancer and greater alcohol consumption, with increases of 32% being observed for the consumption of 35 to 44 grams of alcohol per day, and 46% for the consumption greater than or equal to to 45 grams of alcohol a day, compared to abstainers. However, there were no differences in risk according to the types of alcoholic beverage consumed (wine, beer or spirits). A wine with 12.5% vol. contains 12.5 ml alcohol/100 ml wine x 0.8 g/ml = 10 g alcohol/100 ml wine.

16- Physical activity

Physical exercise lowers the risk of breast cancer, regardless of its weight-reducing effect. Even 40 minutes of walking 3x a week is enough to reduce the risk. Women who practice more intense exercises, such as up to 10 hours a week of walking or 3 hours a week of running, have up to 40% less chance of developing breast cancer.

A recent study published in Cancer Epidemiology, Biomarkers & Prevention found that regular moderate exercise is associated with a lower risk of invasive breast cancer among postmenopausal women. Those who engaged in at least 4 hours of walking per week for 4 years had a 10% lower risk of the disease compared to those who exercised less frequently over the same period of time. The American Society of Clinical Oncology recommends 45 minutes of exercise daily for at least 5 days a week.


17- Pesticides and polluting agents

Pesticides can act as initiators, promoters and accelerators of mutations that give rise to a tumor. This is because toxic environmental substances (xenobiotics) are capable of inducing DNA mutations. Epidemiological studies have documented the association between exposure to pesticides and the development of cancer, in different anatomical locations and age groups, especially in directly exposed agricultural populations, but also by food contamination in urban populations.

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Sorocaba Medical Center


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Tel. 21 2537-0138 / 2539-5093

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Americas Medical City

Barra da Tijuca

Av. Jorge Curi, 550 - rooms 252/253

Tel. 21 3264-4866 / 3264-4863

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