Hereditary Cancer
Each of us has a one in two-lifetime risk of developing cancer, and most cancers are not genetic, but rather they are sporadic and multifactorial or lifestyle related. Some cancers (about 10 percent) run in some families without any obvious genetic link, and in about 10-15 percent there are specific alterations in important genes that are risk factors for developing cancer. This compares to about one in 300 in the general population.
Genes are chains of DNA that code for many important processes within the body. We normally have two sets of genes, one set inherited from our mother and one set from our father. We have about 20,000 genes that have specific important functions. Some genes help protect against cancer by correcting the damage that occurs in the DNA when cells are dividing. Some of the most well recognised genetic risk factors for cancer are faults in genes (mutations) that normally help by repairing faulty cell division and controlling important functions in our bodies.
Breast Cancer
Breast cancer is usually sporadic and affects about one in eight women and is common therefore it is not uncommon to have a relative with breast cancer. Women with one or two family members with breast cancer may have an increased risk up to 30 percent.
About 10 percent of breast cancers, however, are thought to be due to known mutations in specific genes such as the BRCA1 (Breast Cancer 1) or BRCA2 (Breast Cancer 1) genes. Mutations in these genes significantly increase the risk of both breast and ovarian cancer in women and breast and prostate cancer in men by reducing the ability of the cells in these tissues to repair DNA eventually causing normal cells to become cancerous. The table shows the impact of BRCA1 and two on common cancers in men and women.
|
GENE |
BRCA1 |
BRCA2 |
|
Breast cancer in unaffected women (up to age 80) |
60-90 Percent |
45-85 Percent |
|
Women with breast cancer (unilateral) |
50 Percent |
50 Percent |
|
Lifetime risk of a new cancer in the other breast |
Five-year risk of new breast cancer ~10 Percent |
Five-year risk of new breast cancer ~ 5–10 Percent |
|
Ovarian cancer, lifetime risk |
40–60 Percent Risk increases from age 40 |
10–30 Percent Risk increases from mid-late 40s |
|
Male breast cancer |
0.1-1.0 Percent |
5-10 Percent |
|
Prostate cancer |
~10 Percent Similar to population risk |
20-25 Percent |
Thus a woman with a BRCA1 mutation has up to a 90 percent lifetime risk of developing breast cancer and up to a 60 percent risk of developing ovarian cancer. A man with a BRCA2 gene mutation has up to a 10 percent risk of developing breast cancer and up to a 25 percent risk of developing prostate cancer.
Reducing the Risk of Cancer
If a woman knows she carries a BRCA1 or BRCA2 gene mutation there are some risk-reducing strategies she can use to reduce her risk. These include enhanced screening for breast (MRI and mammography) and ovarian cancer, medical treatments (chemoprophylaxis) to reduce the risk of breast cancer and surgery (surgical prophylaxis) to remove the breasts (mastectomy) and ovaries (oophorectomy). Surgery was the much-publicised choice made by Angelina Jolie following her discovery that she had a BRCA mutation. It has also been found that some cancers respond differently to anti-cancer treatments when specific gene mutations are found in them.
Testing in the UK
Currently in the UK BRCA1 and BRCA2 testing is available if the likelihood of being found based your family history is more than 10 Percent. Various online tools have been developed to help calculate that risk. Some other gene mutation tests may also be offered in specific cases depending on family history or diagnosis of a specific type of cancer.
BRCATESTUK however believe that hereditary cancer screening should be made available to everyone who wishes to take control of their hereditary risk for cancer and that the process should have three important stages. Firstly there should be a discussion about the nature of cancer and the role of known genetic risk factors and the relevant family history and also the likely results that might be found and their implications. Secondly, the test can be done using a simple DIY Home Saliva Test with reporting in about 4 weeks. Finally, once the results are available there should be specific genetic counselling about the implications of the results and options for that patient and discussion about the implications for other family members.
The BRCATESTUK service is based on a pre-test consultation, a 30 gene Colour Genomics (www.color.com) hereditary cancer test based on a postal saliva sample and a genetics consultation to discuss the personal and family implications of the results. We are lucky to have the support of some of the UK’s leading Genetic experts to guide us and our patients and we strongly believe in Color’s ethos of democratising access to cancer genetic testing. At an affordable price of £395 we feel BRCATESTUK is one of the UKs most affordable and accessible screening services (www.brcatestuk.com) and the test is also now covered by the leading medical insurance providers in the UK.
See also: Cervical Cancer Awareness
