Breast cancer is the third most common cancer worldwide and the most common cancer in women. The disease is responsible for 23% of all cancers in women.

Worldwide, approximately 1.5 million women per year are diagnosed with breast cancer. In Belgium each year 10500 women are diagnosed. One woman in nine during her lifetime will face the disease. Over the last 30 years we have seen a growing incidence of breast cancer, but the good news is that we have also seen a decreasing number of deaths from breast cancer. This is due to implemented screening and improved treatment options. The impact on health care systems remains immense- for treatment as well as restoration.

Risk factors for developing breast cancer are:

  • Gender: Female gender is the main risk factor, but breast cancer can also occur in men. There is one male patient with breast cancer for every 135 patients.
  • Age: Breast cancer occurs mainly after the age of 55 years, but can also occur much earlier, from the age of 30-35 years. These very young patients are an exception. In fact the curve is bimodal- with the first peak at 50 years (poorly differentiated high grade), and the second at 70 years (slower growing hormone sensitive).  Half of all cases occur in women older than 65. 
  • Hormonal factors: generally one can say that the longer the body is exposed to the influence of the female hormone estradiol, the higher the risk of breast cancer. This means that risk factors are:
    • early puberty
    • late menopause
    • late first pregnancy or nulliparous women
    • oral contraceptives: there is insufficient evidence that the use of oral contraceptives induces breast cancer. Overall, the assumption is that the use of current low-dose oral contraceptives is safe, especially if there is no family risk of breast cancer.
    • hormonal replacement therapy after the menopause: Synthetic hormones can elevate the risk for breast cancer slightly. Natural hormones, which are given in Belgium, do not elevate the risk for breast cancer.
    • prolonged breastfeeding reduces the risk of breast cancer
  • Previous cancer: women with a previous uterine or ovarian cancer have an increased risk of developing breast cancer
  • Previous breast cancer: women who already have experienced breast cancer have an increased risk of developing cancer in the other breast. These women should be offered lifetime screening. Additional risk factors include young age when developing breast cancer, familial breast cancer and the presence of in situ cancers (non-invasive cancers).
  • Ionizing radiation: Exposure to ionizing radiation at a young age (<30 years) or previous irradiation for lymphoma, e.g. Hodgkin’s disease, increases the risk of breast cancer.
  • Moderate alcohol consumption: daily alcohol intake may increase the risk by 40%, but it depends on family history and other dietary factors.
  • Family history of breast cancer: 85% of patients have no family history of breast cancer. When a first-degree relative (mother, sister or daughter) has breast cancer the risk is significantly increased (2x). 5-10% of all breast cancers are hereditary. In these families, breast cancer is very common, and usually develops at a young age. This can often be related to a dominant genetic factor (BRCA1, BRCA2 gene). More info here.

Its greater prevalence in the developed nations suggest lifestyle factors play a significant part.  Rates in the developing world such as the Far East, in Eastern and central Europe are rising rapidly. Within the developed nations, prevalence is lower in areas of social deprivation as many of the risk factors prevail among more affluent populations.