Modifiable risk factors


Several environmental factors are recognized risk factors for cancer.

These include several components related to nutrition, although it is still very difficult to estimate the proportion of cancers directly attributable to them. The risk factors most popular are as follows: smoking, infectious agents, radiation, chemicals. Intake of alcohol is a factor related.

A diet rich in vegetables, fruit and fiber, and regular physical activity appeared to reduce the risk of breast cancer. The consumption of alcohol, a diet rich in saturated fats and animal proteins, and smoking habits, however, will extend it.

  - Active smoking and passive smoking: a study in 3500 postmenopausal women followed for 10 years has shown that the risk of breast cancer is 9% among former smokers (hazard ratio 1.09 (95% CI 1.02 to 1, 17)) and 16% among current smokers (hazard ratio 1.16 (1.00 to 1.34)).

The highest risk of breast cancer was found among women who had smoked for ≥ 50 years or more (hazard ratio 1.35 (1.03 to 1.77) compared to all non-smoking for life, a hazard ratio , 45 (1.06 to 1.98) than non-smokers for life with no exposure to secondhand smoke.

Among women who had never smoked, after adjustment for potential confounders, those with the largest exposure to environmental tobacco smoke ( 20 years' ≥ 10 years' exposure in childhood, ≥ exposure as an adult in the house, and 10 years' exposure ≥ as an adult in the workplace) had a 32% excess risk of breast cancer compared to those that had never been exposed to passive smoking (hazard ratio 1.32 (1.04 to 1.67)).

- Alcohol: one recent study of 109,118 men and 254,870 women, mostly aged 37-70, showed that in Western Europe, a large proportion of cancer cases (5% for the breast) may be due to consumption alcohol, especially with consumption above the recommended maximum limits. These data support the current policy efforts to induce people to reduce or abstain from drinking alcohol to reduce its incidence.  

- Physical activity: Physical activity is recommended to prevent excessive weight gain.

Brisk walking an hour a day or take three to five hours per week of moderate exercise seems to be associated with a lower incidence of the disease.

For most women, moderate to vigorous physical activity such as heavy housework, brisk walking, or dance, may reduce the risk of breast cancer. Over the past 20 years, more than 90 studies have been conducted around the

world and is generally demonstrated an average decrease of 25% risk of breast cancer in women active than the sedentary.

- Diet: diet is regarded as a highly modifiable risk factor for breast cancer, therefore, a strong commitment to understanding how certain dietary factors may promote resistance of mammary epithelial cells to dysregulation of growth.

Adipose tissue is an endocrine organ. The influence of dietary factors on early differentiation of mammary epithelial cells might open new openings in decreasing the risk of cancer. A study in patients whose breast cancer was diagnosed just shows their scheme as having a nutritional diet (very) low consumption of cereals, vegetables, fruit und fish and a high consumption of meat and processed meat.

The consumption of dietary fiber was associated with a significant reduction in mortality from breast cancer. Has also documented the beneficial effect of soy protein, which is expressed by the increase in IGF-1 and IGFBP-3 and the decrease in SHBG (sex hormone binding globulin). The low incidence of cancer and cardiovascular disease in the population around the Mediterranean basin has been linked to eating habits in the region. The Mediterranean diet is rich in nuts, fruits, vegetables, legumes, whole grain, bread, fish and olive oil, with moderate amounts of red wine, which is mainly consumed during meals. Foods rich in BC. omega-3 (fish), oleic acid (olive oil), and phenolic compounds (oil and red wine).

Epidemiological data and animal experiments indicate that dietary fat may influence the risk of breast cancer. EPA and DHA long chain (n-3) PUFA from fish to a large extent, inhibit the proliferation of breast cancer cells in vitro and reduce the onset and progression of breast cancer in laboratory animals. Women with higher intake of EPA and DHA have a food taken as approximate 25% reduced risk of further events in breast cancer [tertile 2: HR = 0.74 (95% CI = 0.58 to 0.94), tertile 3: HR = 0.72 (95% CI = 0.57 to 0.90)] than the lowest tertile of intake. Women with higher intake of EPA and DHA had a dose-dependent reduced risk of all. The intake of EPA and DHA supplements from which the 'fish oil was not associated with breast cancer.

A randomized controlled trial in Canada on 4690 women randomized to an intervention group or a comparison group. The intervention group received intensive counseling to reduce dietary fat intake to 15% of calories and carbohydrates to 65%. However, a significant reduction in the amount of fat in the diet did not reduce the risk of breast cancer in women with extensive mammographic density.

- BMI: it's known from literature that some cancers are more common in obese people than in people with normal body weight.

Approximately 3.2% of newly diagnosed cancers in men and 8.8% in women are associated with high body mass index (BMI). However, many studies suggest a significant correlation between waist-hip ratio (WHR) and risk of cancer compared to BMI. This is in line with the current direction of knowledge based not only on quantity, but especially concerning the distribution of adipose tissue inside a body with a focus on adipose tissue metabolically active.

  Similarly, the pathogenesis of cancer in obese patients is determined by a number of important mechanisms and metabolites, such as insulin, insulin-like growth factor (IGF), insulin resistance, inflammatory cytokines, adiponectin, leptin, and many others. Based on the results of many clinical and epidemiological studies we can say that obesity is considered a risk factor for several cancers, such as cancers of the prostate, breast cancer in postmenopausal women, cancer of 'endometrium, kidney and gastrointestinal cancers (stomach, esophagus, colon). Postmenopausal women who are obese are 50% higher risk of breast cancer compared with non-obese. However, the association between BMI at age 18 and risk of breast cancer in postmenopausal women with histological subtype in the population of the Nurses Health Study showed that teenage obesity is inversely associated with risk of breast cancer both before and after menopause and is valid for that ductal lobular tumors. In prognosis, the risk of developing distant metastasis after 10 years was significantly increased by 46%, and the risk of dying from breast cancer after 30 years was significantly increased by 38% for patients with a BMI of 30 kg / m2 or more. The BMI had no influence on the risk of recurrence, but regional site is endocrine therapy that chemotherapy appears to be less effective for patients with BMI above 30 kg / m2. An independent risk factor in premenopausal women appears to be the circumference of the hips, related to the production of estrogen.

Reproductive and hormonal factors

The early first menstruation or menopause after age 55 are two other predisposing factors.

Motherhood, however, seems to have a protective role: women who have given birth have a lower risk of 25% compared to those who have not had children, and the risk is less, the first occurred the first birth.

The nature of the effects of endogenous estrogens has been difficult to establish. The data are now available from several large prospective studies with biobank of serum preserved, allowing a better characterization of the associations of endogenous estrogens, and other endogenous hormones and risk of breast cancer.

In postmenopausal women, relatively high serum concentrations of estradiol are associated with an increased risk of breast cancer more than doubled, and this probably explains the increased risk in obese postmenopausal women.

In premenopausal women estrogen on the available data are more limited and difficult to interpret because of the wide variations in endogenous estrogens during the menstrual cycle, but are compatible with a positive correlation between estradiol and risk of breast cancer. There is also evidence that the risk of breast cancer is positively correlated with androgens, prolactin and insulin-like growth factor-I. It is estimated that about 190,000 new cases of breast cancer diagnosed in the United States in 2009 alone, 70% will be the bearer of the estrogen receptor mutation. The ER regulates the growth, differentiation and homeostasis of normal mammary gland and its over-exposure to endogenous or exogenous estrogen (E2) is well known to cause breast cancer. Therefore, agents that block or synthesis (ie, aromatase inhibitors) or antagonize the action of estrogen are in clinical use.

Environmental risk

-Pollution: some industrially produced substances and pesticides persist in the environment and focus slowly through the food chain.

The polychlorinated biphenyls are organic compounds used for various industrial uses (paints, glues, etc..) Do not degrade easily. Are more soluble in fats than in water and therefore tend to accumulate, for example, in carnivorous fish such as salmon.

Through these fish can be absorbed by humans and accumulate in the adipose tissue. There is evidence, although very weak, that these compounds may play a role in the development of breast cancer.

- Radiation: is the UV radiation that can cause damage to DNA and thereby acting as potential carcinogens.

Radiation exposure includes radiation used in X-rays for diagnostic and radiation oncology. Radiation exposure increases the risk of breast cancer, thyroid and leukemia.