Complementary Therapies and Cancer: How Much Evidence Is Enough?

We have found some common guidelines that help us determine whether studies and websites can be trusted. We share what we find valuable in a series of blog posts. Andy Jackson, ND, and Miki Scheidel reviewed and provided input on this post.

The lower the risk of harm, the lower the burden of proof.

Donald Abrams, Integrative oncologist and CancerChoices advisor

Burden of proof

Integrative oncologist and CancerChoices advisor Donald Abrams, MD, makes a critical point with respect to complementary therapies: The lower the risk of harm, the lower the burden of proof. In other words, if a therapy is not likely to hurt you, both people with cancer and health professionals may be satisfied with less rigorous evidence that it is effective. 

The burden of proof is lower if a therapy meets these criteria:

1. It is unlikely to do harm.
2. The person considers it affordable.
3. The person is drawn to it or believes it may have value.

Example: A person is having difficulty sleeping. They would like to try acupuncture › to help with sleep. There is some evidence behind acupuncture’s effectiveness for sleep disruption, but it’s not strong. Acupuncture is relatively safe, with few side effects. This person doesn’t have any conditions for which someone may be advised to avoid acupuncture. Because the potential for harm is low, even a modest level of evidence of effectiveness could be enough for this person and their health professional to decide to try acupuncture.

We share the view of Dr. Abrams that therapies that are not especially dangerous and that have credible evidence that they may be helpful do not need as much proof of benefit as therapies that involve more risk or expense. We view the use of science-informedinformed by the most current, highest quality scientific information, but also relying on clinical expertise and experience, theoretical conclusions supported by evidence, and patients’ situations, rights, and preferences, low-risk, affordable therapies as a reasonable option for patients. Stronger evidence of benefit is needed for therapies that are risky, expensive, or otherwise burdensome.

We encourage our readers to consider whether a relatively low level of evidence of benefit
(modestsignificant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) or preliminarysignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently)) is enough to consider using a therapy that may help and is not likely to hurt.

Why evidence may be lacking 

Further, because many complementary therapies involve behaviors and practices and not just pills, designing rigorous, conclusive studies can be difficult. Supplement manufacturers are also not required to conduct research on safety and effectiveness for marketing approval, as drug manufacturers are.

Science-informed therapies

Because the scientific process can be slow to accumulate enough evidence to be conclusive, and because people with cancer often don’t have decades to wait for rigorous research results, science-informedinformed by the most current, highest quality scientific information, but also relying on clinical expertise and experience, theoretical conclusions supported by evidence, and patients’ situations, rights, and preferences therapies are often the only option beyond standard therapies. These might include therapies supported by case studies and observational studies, or for which a strong theoretical rationale exists but full clinical studies are unavailable, incomplete, or inconclusive. Experimental therapies both in conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy cancer care and in complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocialtherapy, and acupuncture medicine can be considered science-informed rather than fully science-based. The level of evidence is far from “good,” but it’s the best we have available right now, at the time you may need to make a decision. 

Keep in mind that at some time in the past every medical treatment now considered conventional was experimental or someone’s best guess as to what might work. Over time, new or otherwise unconventional therapies are researched, and evidence grows that either a therapy does have an effect—and finally it becomes accepted as a conventional treatment—or that it doesn’t work and it remains on the fringes of medical practice.

Other posts in this series