Epidemiological studies have documented extensively the incidence of breast cancer in the Western population but the available information in India is limited and more work needs to be done.
Breast cancer ranks second to all cancer deaths in the middle aged American women, 1,92,200 cases being expected by 2001. One in eight women is affected by breast cancer by the age of 90 years, during her lifetime.
(Surveillance,Epidemiology and End Results) study
reports show that White, Hawaiian and Black women are
at a higher risk of developing breast cancer than Korean, American
Indian and Vietnamese women. The low risk groups are facing an
increased threat of mortality rate than high risk group which remains
stable in recent years .
There are certain mutations which are confined to specific
population. They are called founder
mutations as these mutations arise
from single common ancestor. For example, Ashkenazi
Jews are at more risk of developing breast cancer. Three types
of mutation were found (185delAG, 5382insC in BRCA1, and
BRCA2) in this population. The probability that an individual will
cancer is 56% during
their lifetime. Additional founder BRCA1
mutations (2804delA) were reported in Dutch population
and a BRCA2 founder mutation (999del5) in Icelanders.
|How to read these mutations|
DNA is the hereditary material which carries genetic information
one generation to another. Gene is a part of DNA which gives rise to
functional mRNA which inturn gives rise to a functional protein. DNA is
basically made of 4 nitrogeneous bases A, T, G, C. Gene sequences are read in terms of these 4 letters. The nitrogeneous bases are usually arranged in complementary to one another (A-T,G-C) in a double helical structure. Hence, when there is a disruption in any of these sequences, mutations occur.
So,185delAG means at 185th position in the gene; the bases A and G are missing (deleted).
Similarly, 5382insC means at the 5382nd position there is an insertion of a base C.
6174delT means at 6174th position, there is a deletion of a T.
Cys61gly means at 61st position of the amino acid sequence, cysteine is altered as glycine.
The founder mutations of BRCA1 and BRCA2 in various population are:
|Ashkenazi Jewish||185delAG, 5382insC, 6174delT|
|Austria||2795delA, Cys61Gly, 5382insC, Q1806stop|
|Holland||exon 2, exon 13 deletion|
Breast cancer is the second most prevalent cancer among Indian
women, the first being cervical cancer . One in fifty eight women are
affected by breast cancer in the age group of 30-70 years and are mainly
seen in the urban areas . Male Breast cancer is also
documented in India .
India is a vast sub-continent with a huge population of multiracial society with widely varying cultures, and several ethnic groups. Different aspects of breast cancer involving epidemiology, risk factors and susceptibility have been dealt in various communities and regions.
In India, among the various religious communities studied, Parsis, the followers of zoraster settled in Bombay were found to have four fold increase of breast cancer than the non-parsi population. The order of incidence in other groups is as follows:
A detailed summary of incidence and epidemiological studies are given in the form of table.To view the table, click here