This risk assessment depends upon the number and age of first-degree (mother, sisters, daughters) and second-degree (grandmothers, aunts, nieces) relatives who have had breast or ovarian cancer. Table 10 provides a guide to assessing breast cancer risk.
| High Risk | Medium Risk |
|
4+ relatives
affected at any age (breast or ovarian cancer) 3 relatives affected before 40 years old (breast cancer) 3 relatives affected before 60 years old (breast or ovarian cancer) 2 first-degree relatives with both breast and ovarian cancer Families with Li-Fraumeni syndrome A family member with a positive test for breast cancer genes |
1 first-degree
relative with breast cancer before 40 years old 1 second-degree relative (P) with breast cancer before 40 years old 1 first-degree relative with bilateral breast cancer before 60 years old 2 first- or second-degree relatives with breast cancer before 60 years old or with ovarian cancer at any age 1 first- or second-degree relative with breast and ovarian cancer 1 first-degree male relative with breast cancer |
Patients in the low-risk group (those having one first-degree relative with breast cancer occurring after the age of 50 years) can be looked after by their GP. They will require standard screening mammography every 18 months once they reach the age of 40. Regular self-examination of the breasts is also recommended.
Those women who have a moderate risk of developing breast cancer will be seen in the breast clinic and examined annually. They are advised to have yearly mammography between ages of 40 and 50 and, thereafter, at 18-month intervals.
High-risk women may carry the breast cancer genes BRCA-1 or BRCA-2. These women should be regularly screened for breast cancer from the age of 30 years or even earlier. Screening tools include clinical examination, high-resolution ultrasound scan, mammography (preferably digital) and more importantly magnetic resonance imaging (MRI). The latter has been shown recently to be more accurate than mammography and ultrasound in detecting breast cancer in high-risk young women. However it is more likely to cause false alarms (called false positive results). In relation to high-risk women, it is important to bear in mind the following points: :
- They have a 50% chance of carrying the faulty gene(s).
- If they do carry a gene, it does not mean that they will inevitably develop a breast cancer - only approximately 65% of carriers will develop breast cancer by the time that they reach their 80th year.
- Screening for the faulty genes can easily be carried out if there are living affected relatives who will agree to provide blood samples.
- Doctors are still not certain regarding what is the best course of action to take for an unaffected gene carrier.
Genetic Testing
Before genetic testing is considered, the patient must be counselled regarding the implications of both positive and negative test results, as each result has important implications. Those testing negative, i.e. who do not carry the faulty gene(s), frequently develop feelings of guilt for not having a condition that has affected close family members.
Once a patient has requested a gene test, an affected relative is invited to provide a blood sample. Special scientific investigations are carried out on the DNA in the blood sample, looking for any abnormalities (mutations) in the genes BRCA-1 and BRCA-2. If a mutation is identified, a second affected relative is examined for the same mutation. If both relatives have this mutation it proves that the gene is causing breast cancer in the family. Once this is confirmed, the patient who requested the gene test is then asked to give a blood sample to identify the potential gene.
What Happens if the Gene Test is Positive?
Individuals testing positive for the breast cancer gene(s) have three options:
- Regular clinical examinations and screening mammography on a yearly basis. This method allows earlier detection and treatment of breast cancer. Recent research suggests that magnetic resonance imaging (MRI) is superior to ultrasound and mammography in screening high-risk young women (under the age of 35).
- Surgery to remove both breasts and/or removal of the ovaries. This is an extreme choice but one that is very likely to prolong the survival of high-risk patients. Preventative mastectomy can reduce the risk of breast cancer in high-risk women by 90%. Preventative removal of both ovaries can also reduce the risk of breast cancer by 75% in gene carriers.
- Participation in drug trials. Several studies around the world are currently assessing the role of certain drugs in preventing breast cancer. These drugs include tamoxifen, raloxifene and vitamin A derivatives. Tamoxifen may help to reduce breast cancer risk by approximately 40%, but there is concern regarding its potential side-effects, especially thrombosis and womb cancer.