This is the last of a 3-part series of 'Questions and Answers' on Traditional Chinese Medicine (TCM) and Cancer written by Dr Linn Yeh Ching (Senior Consultant, SGH Department of Haematology).
You may acess 'Doc, can I take TCM for my cancer? (Part 1)' - HERE
You may acess 'Doc, can I take TCM for my cancer? (Part 2)' - HERE
6. But, how safe is it to take herbal medicine together with my ongoing cancer therapy?
This is an important question, but unfortunately one without a satisfactory answer. Potential issues are adverse effect of the herbal product that may affect organ function, and interaction between drug and herb, where one may affect the absorption, distribution, metabolism and excretion of the other. If the chemotherapy drug concentration is reduced due to interaction, its efficacy may be reduced; on the other hand if it is potentiated by the interaction, toxicity may be enhanced. Separating ingestion of herb and drug by 4 hours does not overcome interactions except those that occur in the stomach. However, in most cases interaction occurs at the level of metabolism, or at the receptor / cellular level, where separating the timing of ingestion is not useful. The introduction of targeted therapies with novel agents adds on more unknown factors as some of these agents also have effect on drug-metabolism enzymes which may theoretically be affected by those herbs that potentiate or inhibit these enzymes.
There are no clinical trials dedicated to explore this aspect. At best we can depend on prospective studies with the primary objectives of studying efficacy, for their observations on adverse reaction, where most reported no significant organ toxicity in the TCM group. For drug-herb interaction, except for the cases with single agent, most TCM formulations involve multiple herbs and it is often impossible to find any studies reporting on the same formulation in combination with the same chemotherapy drugs as what a patient is taking, to provide clinical evidence of any potential interactions. Therefore, in terms of drug-herb interaction, there is no readily available answer for each individual scenario, unlike western drugs where there are at least pre-clinical or lab evidence listed in the pharmacopoeia. Expertise in advising such issues is seriously lacking and this is an unmet need ignored by the healthcare system for a long time. We had a Traditional Medicine Information Service under the Pharmacy Dept in SGH which handled enquiries related to traditional medicines, and indeed enquiries on drug-herb interaction was most frequently encountered issue. Unfortunately, this service has stopped operation in 2015 due to lack of funding.
There are some ways to mitigate potential adverse reaction. One is to take TCM under the guidance of a TCM physician with insight in cancer therapy and inform him of the treatment regimen. Another is to inform the oncologist of the consumption of herbal supplement, so that when unexpected observations arise, this possibility can be taken into consideration. It is prudent to withhold the commencement of any complementary therapy to after at least the first 1 or 2 cycles of cancer therapy, in order not to introduce too many new variables at one time. Unfortunately, it is something that you “do it at your own risk”, as such practice falls outside of mainstream medicine in our current healthcare setting.
7. So Doc, will you take TCM if you have cancer?
After saying so much, I have to state my personal position?
To put things into perspectives, for any treatment, the response rate quoted by the doctor is based on statistics derived from other patients with similar condition and given similar treatment. It is just a percentage. To a particular patient, he will either be completely cured, or may relapse, or may not respond at all. The same understanding applies to the use of any complementary treatment, i.e. there is no way to know whether TCM will specifically benefit a particular patient. Here we cite published literature with reasonable standards in order to be as realistic as possible, but it does not imply definite benefit.
Therefore, safety becomes the main factor to consider for any complementary therapy where additional benefit is unpredictable and may or may not happen. Yes, I may take TCM after checking through whatever information I can find and weighing the risk vs benefit, especially after completion of all drug treatment. The decision is more difficult if the treatment involves long term ongoing anti-cancer drugs. By doing so I am making a decision as informed as possible, while doing it at my own risk.
And of course, I will add here that the above are my personal opinion based on my understanding. It is not to be taken as a medical advice to you. It is for your reference only. I wish you good luck
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