Is there a blood test for screening breast cancer?
Women today wonder if there is a simple blood test that will detect presence of breast cancer. This is probably in reference to the CA153 tumour marker for breast cancer that is commonly included in the “package” for screening blood tests. However, this marker is elevated in only 7% of early breast cancer, therefore making this rather useless as a test for screening.
In stage 4 (late stage) cancer, CA153 is elevated in 90% of the patients tested. At this stage, however, the breast cancer is quite obvious even to the patient! Therefore, this blood test would not be necessary to diagnose that a patient has breast cancer. It is useful in monitoring women with stage 4 disease, to see their response to treatment.
However, plans are afoot in Malaysia to study what type of women get elevated levels of CA153. Till more information is obtained through research and studies, for all intents and purposes, there is no blood test for screening for early breast cancer.
What about genetic testing?
Genetic testing – BRCA1 & BRCA2
Testing for genetic defects linked to breast cancer can be both helpful and harmful. If you have a family history of breast cancer, you may live in fear of developing the disease. If the test is negative, it may give you peace of mind. On the other hand, even if a woman tests positive for the defective gene, it may not mean she will get the disease. In the meantime, there may be profound distress.
However, the purpose of testing may be to help a person determine their risk profile and follow prevention and early detection guidelines more rigorously.
Genetic testing is now available in specialised clinics in the West. Ethical issues arise such as preserving privacy as well as ensuring her ability to get health care and insurance in the future, as this may be compromised by advanced knowledge of her cancer risk.
It is a well known fact that the BRCA tests can miss 20% of abnormalities. This means in 20% of those tested, a negative test does not mean a mutant gene is not present. The BRCA gene is a very large gene and testing for it is labour intensive. There are over 50 mutations already described in this gene. Therefore it is not a simple test that can apply for every woman.
The Malaysian Scene
In a recent study “Evaluation of BRCA1 and BRCA2 mutations and risk-prediction models in a typical Asian country (Malaysia) with a relatively low incidence of breast cancer”, published in July 2008 in the international open access journal Breast Cancer Research, project leader, Dr Teo Soo-Hwang, PhD and CEO of Cancer Research Initiatives Foundation (CARIF) reported that up to 9% of Malaysian women who develop breast cancer under the age of 40 years, up to 14% of breast cancer patients who have family history of breast cancer and up to 60% of women with both breast and ovarian cancer had inherited a mutation in one of two specific breast cancer genes, namely BRCA1 and BRCA2.
This genetic change caused each individual to have an 80% lifetime risk of developing breast cancer (compared to less than 5% in the rest of the population) and a 40% lifetime risk of developing ovarian cancer (compared to less than 2% in the rest of the population). The study showed that a proportion of Malaysian women may have inherited a gene from their mother or their father that increased their risk to breast cancer.
Dr Teo concludes that there is conclusive evidence that Malaysians carry similar inherited risks to breast cancer as other Caucasian women.
Counseling before the test is vital
It is important that the patient be counseled adequately as they must understand the implications of a positive test. If they test positive, the risk of cancer is 85% by the age of 65 years.
If positive, prophylactic mastectomy and oophorectomy (removal of ovaries) can be carried out once a woman completes her family to remove the risk of ovarian or breast cancer.
It is probably essential that a specialised genetic clinic for this type of work be set up before even considering routine genetic testing.
Future of genetic testing for breast cancer in Malaysia?
It is too early to tell what is in store for Malaysians at the moment. More studies may need to be done to determine other factors which are integral to promoting routine genetic testing.
Know your breast cancer facts!
CA 153, a tumour marker for breast cancer is only raised in 7% of early breast cancer. It is therefore rather useless as a test for screening.