In 1980, the first gene involved in developing cancer was discovered. This gene is known BRCA1. Normally, this gene is responsible for protecting a women from developing breast cancer so it is called a tumour suppressor gene. Women who have an abnormality of this gene have an increased risk of 56 to 85 per cent for breast cancer and an increased risk of ovarian cancer. This gene occurs in one person in 833. More recently another gene called BRCA2 has been found. This gene has a similar effect and occurs at the same rate as the BRCA1.
Testing for the presence of these genes is currently available in Canada for people who fit within a high-risk category. This testing is usually performed in a genetic testing centre. The test requires a referral from your family doctor.
If breast cancer seems to run in the family, you should talk with your family doctor about your family history. Try to be as clear as possible about the relationships between you and family members who have had breast cancer. The age that your family members were first diagnosed with their breast cancer is also important.
If breast cancer occurs in two or more first degree relatives (a first degree relative includes your mother, sister or daughters), this may mean the disease runs in your family. This would also be possible if one of these first degree relatives had the disease before she reached 50 years of age. Another possible risk would be if a first degree relative had ovarian cancer.
These clues from the family history only indicate a possible increased risk. Many women have mothers, sisters and daughters who have breast cancer. They do not necessarily have an increased risk. Most women do not get the inherited kind of breast cancer.
Two separate genes (BRCA1 and BRCA2) can have abnormalities that increase the risk of breast cancer. These genes are more likely to occur in families of Ashkenazi Jewish descent.
This decision should be made after discussions with your doctor. Talking about the risk of breast cancer and the test is the first step.
You need to consider whether or not it will be helpful to know if you carry a breast cancer gene. Many women want to know, but many do not. These feelings need to be explored and a decision made that is right for you.
Early detection of breast cancer in the normal population can be accomplished by the following:
Early detection of breast cancer in the population known to have increased genetic risk follows the same basic pattern but a schedule will be personalized to meet the needs of each woman:
More accurate information will be available as we continue to learn. Currently we can offer genetic screening to high-risk individuals. Whether or not you want to take part in this is a personal decision. Many women find it helpful to make these difficult decisions in consultation with their personal physician.