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In 2017 David Gorski discussed a study that showed that cancer patients who rely on alternative treatments had a worse survival. He wrote:

…alternative medicine use was associated with a 2.5-fold increased risk of death for combined breast, prostate, lung, or colorectal cancer patients, and a whopping 5.7-fold increased risk of death for breast cancer patients.

Essentially this study suggests that alternative treatments do not work, or at least they do not work as well as conventional treatment. But what about patients who use both conventional and alternative treatments? This David covered in 2018, reporting on another study that showed that cancer patients who use alternative medicine in addition to standard medicine also have worse survival.

When the authors looked at specific cancer types, they noted that the use of CM was associated with poorer five-year survival for breast cancer (84.8% vs 90.4%) and colorectal cancer (81.8% vs 84.4%). However, they did not note any statistically significant differences seen in 5-year survival for patients with prostate or lung cancer.

More data on different kinds of cancer and patient uses would be helpful, but the evidence we have shows that relying on alternative treatments is extremely dangerous, and complementing with alternative treatments does not help, may hurt, and is associated with a higher risk of refusing standard treatment. One aspect of this net negative effect from alternative cancer treatments is the potential drug-drug interactions between over-the-counter (OTC) herbal products and cancer treatments. Oncologists are starting to push back against this trend, warning their patients about possible interactions. Speaking at the Advanced Breast Cancer Fifth International Consensus Conference, Surgeon Prof Maria Joao Cardoso warned about some possible interactions and emphasized the importance of doctors being proactive in asking their patients about herbal product use.

Notice that I referred to these interactions as “drug-drug” interactions. That is because herbal supplements are drugs – they are taken for the pharmacological activity of their constituents. And just like any drug, they can have effects on other drugs and how the body handles other drugs.

Cardoso gives as an example of one type of interaction, herbal products that can potentially cause blood thinning. She lists: green chiretta, feverfew, garlic, ginkgo, ginseng, hawthorn, horse chestnut, and turmeric. Often cancer patients are given blood thinners in careful doses based on the best evidence available. A blood thinner is a great example of the core concept in medicine of risk vs benefit – thinning the blood reduces the risk of blood clots, but also increases the risk of bleeding. Cancer patients often have increased blood clotting and can get complications like deep vein thrombosis (DVT). Blood thinners are used to compensate – but they have to be carefully dosed. Too much blood thinner can increase the healing time of skin lesions and increase scarring. They also increase the risk of hematoma.

Other cancer researchers have also warned about other possible interactions. Antioxidants, for example, are especially problematic. They represent another balancing act critical to cancer therapy – balancing toxicity with efficacy. Chemotherapy is essentially the strategy of giving powerful poisons to patients that kill cells, but they kill cancer cells more than healthy cells. The idea is to shoot for a sweet spot in which the probability of killing all the cancer cells is maximal with the least amount of toxicity to healthy cells. This balancing act is carefully researched and calibrated.

Some chemotherapy drugs work by causing oxidative stress that kills the rapidly dividing cancer cells. This, by the way, is also one mechanism by which your immune cells kill invaders. If a patient takes a high dose of an anti-oxidant in order to reduce the side effects of chemotherapy, they may also be reducing the effects of the chemotherapy. They are adjusting the toxicity-efficacy balance, likely moving away from the carefully researched sweet spot. Add to this the fact that the doses of herbal products are highly variable and poorly regulated, and it becomes impossible to predict what effect such products will have.

Some herbal products may affect the absorption of oral chemotherapy drugs, or affect their metabolism. All of the standard drug-drug interactions are in play.

Another interaction that may be specific to some cancers are hormonal effects:

Botanicals such as red clover and soy products are known to have mild estrogenic effects and may stimulate the growth of hormone-sensitive cancers.

Such products could literally stimulate the cancer to grow, and interfere with standard treatment which is designed to block that very stimulation.

One fairly complicated area of biological activity from herbal drugs is immune function. Many herbal products claim to be either anti-inflammatory (which by definition is immunosuppressive) or to “boost the immune system“. These claims are often vague or even untrue, but the extent to which they are true is likely to be problematic. Immune activity, again, can be a delicate balancing act, even in a healthy individual. The immune system is our body’s army that goes out and kills invaders, but the killing activity often has serious side effects, and healthy cells can get caught in the cross-fire.

There are two contexts here. The first is healthy immune function, in which the immune activity is properly targeted against either infection, foreign bodies, or unhealthy or cancerous host cells. This immune activity is beneficial and we don’t want to interfere with it. However, it can cause unpleasant side effects, such as fever, redness, or pain. How much we can reduce the side effects of inflammation before we reduce the effectiveness of the immune system is a complicated calculation and the focus of much research. For example, the best evidence currently suggests that we should not treat mild fevers, but rather tolerate them as our immune systems do their job. Of course, there are limits – a high fever can be dangerous – and special populations, for example children with fever-induced epilepsy. So complex individual decisions are often required.

On the flip side are “immune boosters”. This does not really exist as a scientific medical concept, because it implies that the treatment is improving the function of the immune system. It is more accurate, rather, to view such effects as shifting the balance toward greater immune activity. In healthy individuals, the balance has been carefully tweaked over millions of years of evolution, so I probably wouldn’t mess with it without good reason and good evidence. In disease states, doing anything to affect the immune system is complicated and even experts guess the net effects of interventions incorrectly. Clinical research has made experts humble about such predictions.

All this does not mesh well with a system in which untrained individuals can treat themselves with OTC drugs making broad and vague claims and that actually affect their immune function. With cancer, we don’t want to impair the body’s ability to fight off cancer cells. With auto-immune diseases, we don’t want to stimulate the immune system further, as it is already overactive. In fact standard treatment is immunosuppressive, again with careful monitoring and balancing beneficial effects from side effects (like increased susceptibility to infections).

One thing to keep in mind is that when manipulating a complex dynamic homeostatic system, such as the body, in either a healthy or disease state, figuring out the net effects of any intervention is extremely difficult. It takes decades of research by experts thinking very carefully to calibrate the proper balance, and then individualizing that information to each specific patient. While doing this, it is generally not helpful for the patient to be interfering with the whole process by taking poorly regulated products often with unknown ingredients, of highly dubious quality control, and in doses that are essentially anyone’s guess.

Further, in medicine there is rarely any free lunch, meaning that any significant medical intervention is a compromise between desired effects and unwanted side effects. We always have to take a careful risk vs benefit approach to any intervention. But herbal products, especially for things like cancer, are often sold with the myth that they are magically free of the compromises that real medicine faces. They are often claimed to magically target cancer cells while leaving healthy cells alone, or “improving” some function when actually they are just pushing a homeostatic system out of balance.

They are also often marketed as “natural” as if that means they operate in some way other than their drug-like effects.

Don’t be conned. Don’t fall for DIY cancer treatment with dubious poorly-studied drugs.

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Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.