Updated 9 July 2014
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) cancers, 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 may come in useful in monitoring women with stage 4 disease, to see their response to treatment.
The American Society of Clinical Oncology does not recommend CA 15-3, CA27.29 or CEA for screening, diagnosis, staging and also for monitoring recurrence (surveillance) after primary breast cancer treatment. The guideline published in 2000 and then in 2007, has not changed with regard these recommendations.
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.
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 a person’s ability to get health care and insurance in the future, as this may be compromised by advanced knowledge of her cancer risk. It is also available in Malaysia in research settings and even commercially in some labs which market the tests directly to the consumer.
Whilst becoming more and more affordable, these “genetic or DNA profiling” tests where it is as easy as sending a blood sample by courier to the company overseas, do not come with counselling or explanation of the findings or the exact type of “genetic” or DNA profiling that is being done.
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 study published in July 2008 issue of the open access journal Breast Cancer Research on “Evaluation of BRCA1 and BRCA2 mutations and risk-prediction models in a typical Asian country (Malaysia) with a relatively low incidence of breast cancer”, 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.
Counselling before the test is vital
It is important that the patient be counselled 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. Whether one wants to remove the breasts with reconstruction is another area of contention. Few women even with a diagnosis of breast cancer are happy to have a mastectomy (surgical removal of the whole breast), more so if it is just a risk of getting cancer over their lifetime.
It is essential that a specialised genetic clinic for this type of work be set up before considering routine genetic testing. It is worse creating anxiety in women who have had a genetic test which does not come with explanation and counselling on their risks as well as level of certainty of accuracy of the tests done.