Antioxidants and Chemotherapy: What You Need to Know Before Combining Them

The scientific paper "Possible Interactions Between Dietary Antioxidants and Chemotherapy," published in the July, 1999 issue of the peer-reviewed journal Oncology(C), has received considerable attention in both the scientific and lay community. Authored by me and Robert Livingston, MD, from the University of Washington Medical Center Division of Oncology, this paper significantly impacts the use of natural medicine during chemotherapy. I will review some of those changes as they affect providers and patients. I will also attempt to answer the most commonly asked questions.

It is important to note that this paper does not address efficacy, even though it references a number of studies showing the positive effects of nutritional supplementation during chemotherapy. It does, however, discuss those circumstances when the use of antioxidants may interfere with the tumor killing actions of some chemotherapeutic agents. It also describes strategies for safely using both.

As a consultant for many area hospitals and transplant centers, our clinic sees a wide variety of patients. One particular case stands as an example. A 12 year-old boy with leukemia had been treated with standard oncology methods, namely chemotherapy. His counts and other prognostic data indicated that he should have had a positive, durable response to the drugs but after his first course of chemotherapy, he unexpectedly relapsed. Treatment was started again, but after a second and third relapse he was transported to Seattle for a bone marrow transplant. His physicians were very surprised that the drugs did not have their anticipated effect and were equally surprised that the patient did not experience the common level of side effects from the chemotherapy protocol.

An alert attending physician suspected that the parents were administering additional, unreported treatments on their own and engaged our clinic in consultation. When I arrived at the hospital, the history was all too familiar. The parents had no less than 30 alternative medicine books as well as a number of suggested treatment plans from "advisors." They were administering a broad combination of therapies in addition to those from the hospital, convinced that these alternative treatments were useful because their son had never experienced the mucositis or other side effects common with his chemo protocols.

The child developed complications secondary to his condition and prior treatment and did not survive long enough to undergo the transplant. This case left many unanswered questions, most notably: Why did a patient who should have done well on chemotherapy fail treatment so badly?

The history provided some clues. This patient was being treated with multiple agent protocols which included alkylators and other drugs. Unfortunately, the supplemental plan administered by the parents included high doses of antioxidants. The fact that the child experienced almost no side effects from this high dose regimen was a clue that perhaps the nutrients had interfered with the actions of the drugs. No other explanation could be found.

The bottom line is that, during chemotherapy and other conventional cancer treatments, common knowledge and intuition may not apply. What is safe and reasonable under almost any other circumstance may be hazardous during conventional cancer therapy. It is the repeat of cases such as this one that motivated Dr. Livingston and I to write this paper.

There are many possible negative interactions between chemotherapy and complementary therapies. Antioxidants are just one example. They depend on the specific agents, the timing of each and the specific status of the patient. These are described in detail in the paper.

In the case of antioxidants and chemotherapy, when there is a negative interaction, the most likely setback will be a recurrence following systemic therapy. In other words, where chemotherapy statistics can predict a 5 year, 10 year or longer remission, the incorrect combination with antioxidants can result in a recurrence before that time. This is based on known, long term human response studies to drug dosage. As the paper also points out, excellent short term results, even as long as a few years, may mask a worse long-term outcome.

The most common questions from providers and patients are answered below:

Q: Does this mean that antioxidants are a bad thing during cancer treatment?

The answer depends on timing. During certain chemotherapy (and some other treatments) the ability of antioxidants to quench free radicals can interfere with the established tumor killing mechanisms of these conventional treatments. This applies to certain drugs and treatments and is definitely a dosage related process.

Q: Does this mean that antioxidants should never be used with chemotherapy?

It does not mean that. Once again, the answer depends on the specific agents as well as dosage. The paper answers this question in detail as well.

Q: How much do we actually know about this process?

The journal paper has a thorough bibliography. In summary, there are excellent long term human studies describing both the pharmacology of the drugs, the chemistry of oral antioxidants and some combinations. We know that the most likely risks for interference are long term, 5 to 10 year relapse rates, when incorrect combinations are made with high dose, systemic therapy.

This can be very confusing for those not familiar with the long term data on these chemotherapy programs. In vitro, animal and shorter term human studies will predictably show improved results when combining antioxidants and vulnerable chemotherapy agents because they do not address the long term kinetics.

Q: Now that I understand all this, how do I treat patients on chemotherapy?

The answer is pharmacological and is described in detail in the journal paper. In short, only utilize antioxidants when the vulnerable drug is not active at the same site of distribution. When in doubt, don't. It is hardly worth risking a cancer recurrence for a small improvement in short term results.

Keep in mind that the antioxidants are just one potential source of interaction with conventional cancer treatment. There are many others and I encourage you to learn as much as possible about both the conventional treatments and complementary treatments, including their pharmacokinetics and pharmacodynamics, before prescribing concurrently. Some of the mechanisms of interaction are clear while others are just suspected. Our policy has always been to err on the side of patient safety. It is possible to take advantage of the many positive effects of natural medicine and still avoid the potential pitfalls of incorrect combinations.

If you have questions about the journal paper or its implications, feel free to contact the undersigned or one of my colleagues at the clinic, John Sherman, ND, or Carol Collins, MD, preferably by fax. We commonly answer such questions and, if you wish, we have an established reasonable consult program to support providers developing adjunctive plans for specific patients.

If you want to learn more about this subject, you can request a reprint of this paper from the publishers of the journal: PRR, Inc., 48 South Service Road, Melville, New York 11747 USA.

You can also request an official reprint from our office.

Article copyright Townsend Letter for Doctors & Patients.


By Dan Labriola

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