Epidemiology of breast cancer

Epidemiology of breast cancer

Epidemiology of breast cancer

Read Breast Cancer first.

  • It is estimated that, worldwide, more than 1 million new cases of breast cancer are diagnosed yearly.
  • The incidence and death rates for breast cancer differ between races but the rates are more common in the Western nations and lowest among the developing world.
  • About 1% of breast cancers is found in males and 90% are estrogen receptor (ER)-positive
  • The risk of breast cancer increases with age
  • The genetically defined group of women with BRCA-1 or BRCA-2 identified to carry lifetime risk of as high as 80%. Women who carry a germ line mutation in BRCA1 genes have a cumulative lifetime incidence of 50% to 85% of developing breast cancer and 40% to 60% of developing ovarian cancer

Genes and breast cancer

The genetically defined group of women with BRCA-1 or BRCA-2 identified to carry lifetime risk of as high as 80%. These genes function in cells in a variety of ways such as

  1. Repair of damages DNA
  2. Cell-cycle regulation
  3. Transcriptional regulation
  4. Remodeling of chromatin in cells. Chromatin are the gene carrying vehicles in all cells
  5. BRCA-2 is involved primarily in DNA recombination and repair

The reason why these genes predispose primarily to breast cancers remains unknown. BRCA1 and BRCA2 genes can be carried and passed to children by men as well as by women. A drug tamoxifen has been shown to reduce the risk of contralateral breast cancer by about 50% in both BRCA1 and BRCA2 carriers.

The characteristics of BRCA1 and BRCA2 genes

  • BRCA-1 is located in chromosome 17 where as BRCA-2 in chromosome 13
  • The percentage contribution of BRCA-1 genes to hereditary breasts cancer is about 20 to 40% where as the BRCA-2 is 1- to 30%
  • The lifetime risk of developing breast cancer with is 60 to 85% in both genes
  • The lifetime risk of developing secondary breast cancer is about 50% in both
  • The risk of developing male breast cancer is minimal in BRCA-1 and about 4-6% in BRCA-2 genes
  • The risk of developing other types of cancers such as the cancer of the prostate , pancreas , stomach, ovary and melanoma

HER2 genes

Another gene, HER2 presents with its protein over expression in 20% of newly diagnosed breast cancers. HER2 stands for Human Epidermal growth factor Receptor 2.

HER2 gene positive breast cancer is associated with a more aggressive clinical course and decreased survival time compared to tumors with normal levels of HER2. Each normal breast cell contains copies of the HER2 gene found in the DNA of the cell. HER2 contains information that helps to make HER2 proteins.

The HER2 protein is the HER2 receptor found on the surface of some normal cells in the body. The proteins help send growth signals from outside the cell to the inside of the cell and pass the message for cells to grow and divide.

In HER2+ breast cancer, the cancer cells have an abnormally high number of HER2 genes per cell. When this happens, too much HER2 protein appears on the surface of these cancer cells. This is called HER2 protein overexpression. This causes the cells to grow and divide more aggressively. This contributes to growth autonomy and genomic instability where the cells growing hev no control at all.
Symptoms of breast cancer

  • Breast cancer is usually first detected as a palpable mass or as a mammographic abnormality. These masses and areas of asymmetrical thickening of breast tissue are the most common manifestations of breast cancer.
  • There is nipple discharge, retraction and flattening of the breast. Spontaneous bloody or watery discharge from the nipple is commonly associated with underlying breast neoplasm. Presence of milky discharge almost always has a noncancerous cause.
  • Changes in the skin over the breast. There is skin swelling, and erythema.
  • Breast pain. the breast pain typically is associated with a palpable lump
  • Paget’s disease of the nipple is a form of adenocarcinoma involving the skin and lactiferous sinuses of the nipple; it usually appears as an eczematous lesion of the skin of the nipple. It’s frequently associated with excoriation of the skin and discharge.
  • Lumps in the armpits and above the clavicles

Breast Cancer

Breast Cancer

Breast Cancer

Definition

Breast cancer is an invasive cancer of the breast affecting both men and women. The local cells of the breast grow abnormally and uncontrollable increase in size and spread to other area s of the body.

Other names

Carcinoma of the breast

What causes breast cancer?

Various causes of breast cancer have been explained, but the exact cause is still unknown. There are numerous risk factors that increasingly relate to the development of breast cancer such as:

  • The increase in age of a person. It is estimated that close to 50% of women with breast cancer in the western world are more that 60years of age
  • The earlier a girl gets in to menarche especially at <12 year, the higher the risk of developing breast cancer.
  • When approaching menopause late especially at over 55 years, one has an increased risk of developing breast cancer. This is an indirect cause.
  • The increasing the number of menstrual cycles could predispose women to greater DNA damage in the proliferating breast ductal tissue and thus could increase the risk of mutations that directly lead to breast cancer.
  • Child bearing at a later age is a predisposing factor to breast cancer in women.
  • Any form of benign breast tissue disease may increase the risk of cancer
  • Women who live sedentary lifestyles and do not exercise often are at an increased risk of developing breast cancer
  • Breast cancer has been associated with women who live in upper socioeconomic classes. This may also be associated with more sedentary lifestyles
  • Personal history of breast cancer (in situ or invasive)
  • Postmenopausal hormone replacement treatments with estrogen hormones (with or without progestin) have been shown to increase the risk of getting breast cancer. The risk is increased by about 1.5times
  • Developing obesity after menopause increases the risks of breast cancer in women
  • The use of oral contraceptives increases breast cancer risk minimally if at all. It is t known whether estrogen replacement alone increases risk. However there is a much more increased risk in using these hormones in leaner postmenopausal women. The exact mechanism of cancer formation is unknown but there is a possibly of interaction of ovarian estrogen and other types of estrogens of external origin with breast tissue that leads to susceptibility to develop cancer of the breast
  • Alcohol is also associated with increased risks of developing breast cancer. Surveys show that moderate alcohol intake (two to three drinks/day) has a 1 to 1.8 times the risk of developing cancer.
  • Diet effects. Increased estrogen levels have been found in women with a higher BMI. These pose as an increased risk of developing breast cancer.
  • Family history of breast cancer is a risk factor in women. The risk in first degree relatives is 2 to 4 times more. Having relatives of known high risk factors also play a role. Having two first degree relatives with breast cancer increases the risk by 5 times.
  • Women with an increased bone density have been shown to have a risk of developing cancer.
  • Having children at a later age of more than 30 years poses as a risk to women to develop breast cancer. There is even an increased risk in non-child bearing women ( nulliparous)
  • Women with a personal history of endometrial cancer do have a risk of developing breast cancer.
  • Women with larger breast masses have a more breast density that increases the breast cancer risk. The density can be shown through mammography
  • Exposure to radiation to the chest poses as a risk of developing breast cancer in women.
  • Women with an established breast cancer gene BRCA-1 and BRCA-2 are associated with high risk of developing the cancer

Continue reading Epidemiology of breast cancer.