04/06/2013
Thus Spake…Prof. Rossa Chiu on Genetic Diagnosis
Please tell us something about your current research.
I'm primarily analysing the DNA materials in human blood samples, expanding the applications of blood tests with an aim to replace the need to collect biopsy samples which has a much higher risk. Conventionally, it was thought that organ tissues were required for DNA diagnoses. But in fact when cells die due to natural metabolism or illness, metabolic substances remain in the blood plasma. In 1997, Prof. Lo Yuk-ming Dennis discovered the presence of fetal DNA in the maternal blood plasma, and pioneered the use of such markers for fetal DNA diagnosis. In 2008, a non-invasive prenatal test for Down syndrome was developed, achieving a 99% accuracy within a short time. A convenient mode of application was soon found and the test is now used in many parts of the world. In 2010, we can decipher a genome-wide genetic map of the fetus through the analysis of the small amounts of fragmented DNA in the maternal blood. This allows us to develop non-invasive prenatal diagnostic tests for multiple genetic diseases in a non-invasive way. Currently, we can reconstruct genetic maps of liver, breast and ovarian cancer using blood samples. The aim is to develop methods for screening cancer and genetic mutations, that are non-invasive, widely applicable, and can be frequently carried out.
In the wake of the so-called Angelina effect, what is the role of the medical practitioner in advising people considering such 'preventative' actions?
Medically, Angelina Jolie's case is nothing new. Preventive organ removal has been accepted as a method of treatment for 20 years. Her uniqueness lies in publicizing her decision and the surgery. By doing so, she raises awareness of genetic diagnosis, and draws attention to the ethical principles doctors should have. Firstly, doctors should be knowledgeable about genetic disorders. Breast cancer is one of the main killers of women. About 10% of cases are caused by a BRCA1 gene mutation. People with the mutation have a probability of 80% and 40% respectively, of developing breast cancer and ovarian cancer before age 70. Those also harbouring the risk include the mother, sisters, maternal grandmother, daughter, even male members of the family. Doctors should tell patients with a family history of breast cancer about the BRCA1test. Secondly, there should be adequate counselling, clear explanation of the test's limitation and what different results entail. For example, if the result is positive, family members may be under pressure to take the test. Thirdly, doctors should explain the pros and cons in detail—by how much surgery would reduce the risk, the surgical process, its potential physical and psychological effects, so that patients are well informed about whether they should take the test or undergo the surgery.
[Original source: Newsletter on 4 June 2013, CUHK Information Services Office] Website http://www.iso.cuhk.edu.hk/english/publications/newsletter/article.aspx?articleid=56625