Medical myth: natural cancer therapies can't harm you

One of the most misleading myths of modern medicine is that conventional cancer doctors reject "natural" therapies in favour of artificial or "unnatural" cancer treatments. This myth has contributed to the popularity of unproven, alternative cancer treatments.

The truth is that oncologists and other trained medical professionals involved in cancer care welcome and support effective cancer treatments in any form, provided there is evidence to show they can work and are safe.

Making assumptions about the benefits and harms of therapies according to whether or not they are natural is high-risk. For example, laetrile, an extract from apricot kernels, was for years promoted as a natural alternative therapy for cancer; yet it is utterly useless for treating cancer and can cause fatal cyanide poisoning.

The herb comfrey, also recommended as an alternative cancer treatment, actually causes cancer.

So natural does not necessarily equate to harmless. Nor does conventional necessarily equate to unnatural. Plenty of natural products are used in chemotherapy. These include extracts from the yew tree (docetaxel, paclitaxel), the opium and mandrake plants (epipodophyllotoxins) and from natural moulds that produce doxorubicin and related drugs, used effectively to treat breast cancer and lymphoma.

Some natural products used in conventional cancer medicine had for centuries been part of traditional folk remedies and have been adapted for modern use after being rigorously tested.

So the difference between alternative and conventional is not that one is natural and the other is not. It's that conventional cancer treatments must be subjected to rigorous research before they can be recommended for use and prescribed by professional oncologists.

The highest level of research is the randomised control trial, which is only applied to a product after lengthy laboratory studies, preliminary testing and approval by an ethics committee made up of medical experts, ethicists and healthcare consumers.

A typical trial involves randomly selecting two groups of patients in large enough numbers to control for physical differences between them. One group receives the new treatment and the other group is given a different treatment or a placebo; the results are then compared. A trial is designed to show that any significant difference in patient outcomes can only be the result of the treatment being tested.

Oncologists will only prescribe treatments if they have been tested in this way and are found to be effective and safe.

A good example of this testing process on a natural derivative is the development of the drugs vincristine and vinblastine, extracted from the Madagascan periwinkle. Improved through continual clinical trials over 50 years, these so-called "vinca" alkaloids have been a key part of modern-day successes in curing childhood leukaemia and other cancers that were previously incurable.

Some alternative cancer therapists also promote fad diets, but there is no evidence to support this approach. A healthy diet can prevent cancer and assist people living with cancer. But diet will not cure cancer, which directly attacks the body's cells in a highly destructive and relentless way.

Such a malignant disease can only be cured if the cancer cells are surgically removed before the cancer has spread or if they are destroyed with chemotherapy and/or radiotherapy.

Nor is there any evidence to support mind control in any form as a cancer therapy. Such a belief or expectation in many cases adds to a patient's distress. Can you imagine the terrible trauma of being diagnosed with a potentially fatal cancer and told you can think your way to good health with a positive attitude?

The reality is, we have a limited lifespan; science does not have all the answers to our health needs. But we agree as a society that we should do what we can to increase life expectancy and improve health.

Over the past century, average Australian life expectancy has increased by almost 30 years, largely through a combination of improved infection control, sanitation, diet, immunology and many other advances in medical science.

The changes in medical practice and public policy that have improved our length and quality of life were guided by evidence of what works.

So we must let the evidence - not uninformed perceptions of what is natural guide continuous improvements in cancer treatment.

This blog also appears on The Conversation.