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The safety of complementary and alternative therapies

Some therapies may be harmful or could interact with other treatments you're having. Talk to your doctor before starting any complementary or alternative therapy.

Safety of complementary therapies in cancer care

Many complementary therapies are safe to use alongside conventional cancer treatments, such as radiotherapy or chemotherapy. Most doctors will support you using one or more types of complementary therapy.

Some complementary therapies can help people to feel better. Some help to reduce symptoms and side effects. But some types might not be safe in certain situations. For example, some might stop conventional treatments working as well as they should.

There is a concern that taking antioxidants (which includes vitamins A, C and E, and selenium) while having chemotherapy or radiotherapy could actually protect cancer cells from being damaged by the cancer treatment. There is not enough evidence to know whether antioxidants are helpful or harmful in this situation. We need more research to help us learn the best ways to use complementary therapies.

The safety of any complementary therapy will depend on what it is, and on the type of conventional treatment you are having.

Remember that complementary therapies might have side effects. It's important to know what the possible side effects are before you start using them.

Talk to your doctor about any complementary therapies you're thinking of using. Tell them before you start having complementary therapy, especially if you're in the middle of a course of cancer treatment.

Make sure you also tell your complementary therapist about your cancer treatment.

Safety of alternative cancer therapies

Some alternative therapies might be harmful and cause side effects. They might interfere with your conventional cancer treatment.

Therapists and companies who promote alternative therapies can cause harm by convincing people an alternative therapy will cure them when it can’t. This can be especially harmful if a person is also encouraged to give up their conventional cancer treatment.

Lack of scientific evidence

There is research into various types of alternative therapy. But there is no scientific or medical evidence to show that they can help to treat or cure cancer.

Therapists and companies who promote alternative therapies often rely on the reports of individual experiences from people who say a therapy has helped them. For scientists and cancer doctors, this is not enough to prove anything.

New therapies and potential cancer treatments must be compared against accepted and proven ones so that we can be sure of their benefit. The best way to do this is by running organised clinical trials. This is how conventional cancer treatments are tested.

Money making schemes

Unfortunately, some alternative therapies are just money making schemes. People can end up paying a great deal of money for something that has not been properly tested, or has not proven to work in scientific studies or clinical trials.

This is very unfair on people with cancer. They might be vulnerable and willing to try anything they think has a chance of curing the cancer. This is one of our main concerns.

Our message is:

  • be very careful
  • make sure that you look into the information that is available
  • be wary of anything you find for sale on the internet
  • talk to your own cancer doctor before you buy anything

Talk to your treatment team first if you think you want to stop conventional treatment to try an alternative therapy. Even when conventional treatment can no longer cure a cancer, your doctor can help control symptoms such as pain and sickness by giving you conventional medicine.

Telling your doctor about using a therapy

Tell your cancer doctor, specialist nurse, pharmacist or GP if you are considering using an alternative therapy or complementary therapy. Many people don’t mention it simply because their doctor does not ask. Or they worry their doctor will tell them to stop using the therapy.

Complementary therapies

It is very important to tell your specialist team because some therapies might interact with your conventional cancer treatment. They might make them work less well or increase the side effects. You need to be especially careful with some dietary supplements such as vitamins, minerals and herbal products.

Most doctors will support you using a complementary therapy if they think that it's safe for you to use. They might not know much about the specific therapy you are using or want to use. But, they might be able to find out more. You might be able to teach each other.

Some health professionals find it helpful to have a letter from the therapist that gives more details about the complementary therapy. Your doctor will discuss any concerns they have about the therapy with you.

Make sure you also tell your complementary therapist about your cancer treatment.

Alternative therapies

Because there is a lack of evidence that they work and we don't know much about the side effects, your doctor may advise you against using certain types of alternative therapies.

Giving up conventional treatment to use an alternative therapy

Talk to your treatment team first if you think you want to stop conventional treatment to try an alternative therapy.

Of course the final decision rests with you. But your doctor can explain that there is evidence that conventional treatments can treat or control your cancer. There is no evidence that alternative therapies can cure or control cancer.

Your doctor will not try to stop you using something that you think might help you. They will explain the possible risks and will always act in your best interests. They'll also try to make sure that you have considered every possibility available to you.

Even if your doctor doesn’t agree with your decision to start an alternative therapy, they will respect it and acknowledge that using an alternative therapy is important to you.

But they may suggest that you should restart your conventional treatment if the alternative therapy has had no effect on the cancer within a set time. It's important to give this some serious thought.

Remember that there is a big difference between a therapy having a physical effect on your cancer and it making you feel better.

Last reviewed: 
23 Oct 2014
  • Oxford Textbook of Palliative Medicine (3rd edition)
    D Doyle, G Hanks, N Cherny and K Calman
    Oxford University Press, 2005

  • Eyes on Evidence: Drug interactions associated with herbal remedies and dietary supplements
    National Institute for Health and Care Excellence, 2013

  • Spontaneously reported adverse reactions in association with complementary and alternative medicine substances in Sweden
    I Jacobsson and others
    Pharmacoepidemiology and Drug Safety, 2009. Volume 18, Issue 11

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