Breast cancer arises in the tissues of the breast, most leading cancer among females. About 1% of breast cancer is found in males too. Breast cancer is the second most common malignancy among women, next to cervical cancer. Breast cancer is the second leading cause of death by cancer in women, following only lung cancer.
The global burden of the disease was up 22 per cent, in incidence and mortality, compared with 1990 and is set to increase by 50 per cent over the next two decades, according to the International Agency for Research on Cancer (IARC) in Lyon, France. Breast Cancer is the most frequent cancer in women worldwide with 1.05 million new cases every year and represents over 20% of all malignancies among females. Over 50% of breast cancer incidence occurs in the developed world in countries of Europe and North America while lowest rates reported from African and Asian countries. However, incidence of breast cancer is increasing in most of the countries, including those, which have had previously low rates. Breast cancer is only a risk for half the population women yet it is the second most common cancer in the world after lung cancer. Because survival prospects are good compared with other cancers, there are 3.9 million women alive who have had the condition diagnosed within the past five years, more than for any other cancer. However, the disease still claims 370,000 lives a year, accounting for 13.9 per cent of cancer deaths among women.
Breast cancer usually affects tissues involved in milk production (ductal and lobular tissues). The cause of most breast cancers is unknown; however, a small percentage of breast cancers tend to cluster in families.
Breast cancers can occur even at early age as hereditary breast cancers, caused by inherited gene mutations and are more likely to involve both breasts. The breast cancer risk in female first-degree relatives is estimated to be 2.4 times the risk in the general population.
Today, medical scientists can pinpoint mutations in individual genes which increase breast cancer risk. While these mutations do not account for all cases of breast cancer -- there are other factors remaining to be explored -- the presence of the mutations offers a more accurate picture of a person's risk for breast cancer. Some of these mutations are passed down through families and ethnic groups.
Variations of the ATM, BRCA1, BRCA2, CHEK2, and RAD51 genes increase the risk of developing breast cancer. The AR, DIRAS3, ERBB2, and TP53 genes are associated with breast cancer.
BRCA1 and BRCA2 are major genes related to hereditary breast cancer. People who have inherited certain mutations in these genes have a high risk of developing breast cancer, ovarian cancer, and several other types of cancer over their lifetimes. Men with BRCA1 mutations have an increased risk of developing prostate cancer. Mutations in the BRCA2 gene are associated with an increased chance of developing male breast cancer and cancers of the prostate, pancreas, gallbladder, bile duct, and gastrointestinal tract. Melanoma (an aggressive form of skin cancer) and lymphoma (a cancer of immune system cells) also are more common among people who have BRCA2 mutations.
The breast cancers can be caused by mutations in particular genes, such as BRCA1 or BRCA2. BRCA1 and BRCA2 are genes which are involved in the immune system's tumor suppression function; mutations in these genes lead to increased cancer susceptibility. The risk of breast cancer in women who inherit a germline mutation in the BRCA1 gene can be as high as 20% by the age of 40 and 50% by the age of 50 and as high as 13% by the age of 40 and 60% by the age of 50 in BRCA2 mutation carriers.
In some cases, genetic syndromes involving other cancers also include an increased risk of breast cancer. The prevalence of inherited BRCA1 and BRCA2 mutations in the world population is lower, 0.1 to 0.2 percent. These mutations are implicated in about 10 percent of all cases of breast cancer.
Carriers of a BRCA1 mutation alone are thought to have a very high -- 50 to 85 percent -- lifetime risk of breast cancer and a 20 to 40 percent lifetime risk of ovarian cancer. Women with a BRCA2 mutation alone appear to have similar risk of breast cancer and a 10 to 20 percent risk of ovarian cancer. Familial cancer tends to occur at a younger age than non-familial cases. However, the increased risk in women with both of these mutations is lifelong.Recent advances in genetics now enable many women -- and men -- to gain a much clearer picture of their and their children's risk of developing cancers such as breast and ovarian cancer. Armed with this knowledge, there is a case to be made out to diagnose which individuals are likely to be afflicted by a particular cancer through the usage of molecular diagnostics.
The main treatments for breast cancer are:
- Surgery
- Radiotherapy
- Hormone therapy
- Chemotherapy
- Targeted drug therapy - Eg: trastuzumab (Herceptin) and Lapatinib (Tykerb)
Lapatinib (Tykerb), a new molecular entity (NME), is a kinase inhibitor that works on multiple targets to deprive tumor cells of the signals needed to grow.Unlike, Trastuzumab (Herceptin) - which is a large protein molecule that targets the part of the HER2 protein on the outside of the cell - Lapatinib is a small molecule that enters the cell and blocks the function of this and other proteins.Because of this difference in action mechanism, Lapatinib works in some HER2 positive breast cancers that have been treated with Trastuzumab and are no longer benefiting from treatment.
