by Dr. Albert Lim Kok Hooi
Metastatic breast cancer (MBC) is breast cancer that has spread to the bone, lung, liver, brain and other organs. The median survival for patients a decade ago was 24 months. In other words, half the patients lived for less than 24 months and the other half survived more than 24 months. Few patients survived more than 5 years.
Today, the median survival for MBC is more like 36 months. In fact, a fortunate few may live up to 10 years or more.
How did this come about? The answer is simple : well-conducted laboratory research has led to a better understanding of the biology of breast cancer and more effective drugs with lesser side-effects.
The important first step in treating MBC is to test the tumour for the HER2 oncogene. About 25% of breast cancer patients have tumours which over-express this oncogene. These tumours behave aggressively. If the tumour is tested positive for the HER2 oncogene, the drugs of choice are trastuzumab and/or lapatinib. These are anti-HER2 drugs in routine clinical use.
Many more drugs in this class will come on line in the next few years. Anti HER2 drugs is usually combined with conventional chemotherapy or with each other depending on the circumstances.
If the breast tumour is HER2 negative (that goes for about 75% of patients with MBC), we want to know if the tumour bears the estrogen receptor (ER) and/or the progestogen receptor (PR). If so, hormonal therapy is usually used.
Today, we have many hormonal agents that can be used one after another. In medical parlance, they are used sequentially. We use tamoxifen (the most common hormonal therapy for breast cancer) and when this is no longer effective, the aromatase inhibitors (A.I) is used. There are three drugs in this class : anastrozole, letrozole and exemestane. They are used only in post menopausal women.
Finally, we have fulvestrant, which can be used when A.I is no longer work. These hormonal therapies are 'gentle' and without the usual side-effects associated with chemotherapy.
Let us pause for a while and move away from the world of drugs, which can be intimidating to some. The way of thinking about cancer treatment is the algorithmic way. It is based on an algorithm. We think algorithmically.
Simply put, it is like walking along a country road and meeting a fork. If HER2 is positive, I take the left lane. If not, I take the right. I go along the right lane and meet a second fork. If ER is positive, I take the left path. If ER is negative, I take the right and so on and so forth.
So much of life is and all of computer programming is algorithmic. It is really quite simple if you think about it.
Back to MBC. If the tumour is HER2 negative and ER negative, chemotherapy will be employed. At least 8 drugs can be choosed from. Newer chemotherapy agents are more effective and have lesser side-effects. We now have many new therapies to deal with the side-effects of chemotherapy. For example, low red blood cell counts and low white blood cell counts are better managed. We also have very effective anti-vomiting drugs.
Recently, another drug was introduced for routine clinical use in treating MBC. Bevacizumab is a drug which inhibits new blood vessel formation (angiogenesis), which is a crucial process in cancer growth, proliferation and spread.
To recap, 4 classes of drugs to treat MBC are used. They are (i) anti-HER2 agents (ii) hormonal therapies (iii) conventional chemotherapy (iv) anti-angiogenic agents.
To be sure, not all 4 classes of drugs are suitable for all patients. The important thing is to seriously consider all of them. For any patient, pick the most suitable combination and the most logical sequence of the classes of drugs we discussed.
My oncologist colleague and I were privileged to celebrate Hari Raya with a patient with MBC who has gone through all the 4 classes of drugs. She is leading a good meaningful life 6 years after the diagnosis of MBC. She is living comfortably with MBC, not dying of it.
She is a true beneficiary of scientific research. She is not alone. The future is bright. More research will result in more drugs. The median survival for MBC may soon be 48 to 60 months.
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