Do you look forward to that end-of-day glass of red wine, like I do? Do you seek out those medical articles that support the notion that a glass of red wine, in moderation, protects the heart, reduces obesity, prevents cancer and minimizes the effects of global warming? (OK, I found the latter one on a blog.) While there is great discussion about whether we should drink a glass of red wine versus a glass of grape juice, what is not debatable are the health benefits of their antioxidants. However, there is an explosion of products on the market that seek to improve the health and well being of people using nutritional supplements. More and more often, pet owners are seeking the same products to complement or serve as an alternative to traditional forms of cancer therapy. There is concern among oncologists that antioxidants may reduce oxidizing free radicals created by radiotherapy and some forms of chemotherapy, thereby decreasing the effectiveness of the therapy. Maximizing Cell Damage Dietary and endogenous antioxidants prevent cellular damage by reacting with and eliminating oxidizing free radicals. However, in cancer treatment, a mode of action of certain chemotherapeutic agents involves the generation of free radicals to cause cellular damage and necrosis of malignant cells. So it is natural to be concerned as to whether exogenous antioxidant compounds taken during cancer therapy could reduce the beneficial effect of therapy on malignant cells. Yet there are animal studies demonstrating decreased tumor size or increased longevity with the combination of chemotherapy and antioxidants. Similar studies in human beings using combination chemotherapy showed that the use of a combination of antioxidants, vitamins, trace elements and fatty acids prolonged patients' survival time. While it is known that the oxidative mechanisms of alkylating agents create substantial DNA damage - resulting in cell necrosis - recent evidence indicates that a sizable amount of chemotherapy damage is induced by other mechanisms, which trigger apoptosis (programmed cell death). Various antioxidants have been shown to increase cell death by this same mechanism. Given this, any argument that antioxidants are likely to interfere with most chemotherapy is too simplistic and probably untrue. A commonly cited 1998 study warned that CoQ10 reduced the effect of radiotherapy on small-cell lung cancer in mice. This trial did, indeed, show a significant inhibition of radiation-induced cell growth delay at 40 mg/kg oral dose, and a borderline inhibition at 20 mg/kg. What About CoQ10? However, no inhibitory effect on radiotherapy was noted at 10 mg/kg CoQ10, a dose roughly equivalent to 60 mg in a 60-pound dog. The normal animal dose recommendation of CoQ10 of 30 to 60 mg/day probably has little inhibitory effect on concurrent radiotherapy. Because of the cardiotoxic effects of doxorubicin, a potent creator of oxidative radical species, a number of studies have looked at the prevention capacity of CoQ10. A small study in humans showed CoQ10 administered at 1 mg/kg led to a more than 20 percent reduction in episodes of ECG change post-treatment, compared with doxorubicin alone. Diarrhea and stomatitis were also significantly reduced. A mouse study confirmed the protective effect of CoQ10 treatment on the toxicity of doxorubicin. In this study, it was noted that CoQ10 did not reduce the anti-tumor effect of doxorubicin. Instead, a trend toward better tumor control was seen. Friend or Foe? The attitude of many conventional practitioners toward antioxidant therapy for cancer has been hostile. Others have raised the argument that antioxidants could blunt the effect of standard therapies, particularly alkylating, platinum and tumor antibiotic agents, which are oxidative in nature. While this appears a theoretical concern, the evidence shows that this proposed interaction of anti- and pro-oxidant therapies is not generally of primary importance in vivo. Contrary to conventional wisdom, the effects of using antioxidants concurrent with chemotherapy and radiation are synergistic. There is no evidence to date showing that natural antioxidants interfere with conventional cancer therapeutics in vivo. In well-controlled studies, human patients treated with antioxidants, with or without chemotherapy and radiation, have tolerated standard treatment better, experienced less weight loss, reported a better quality of life, and most importantly, lived longer than patients receiving no supplements. As a profession, we must continue to critically review the latest available research that reports the positive interactions existing between antioxidants and chemotherapy or radiation. It is time to research the role of these agents in conventional oncologic treatment, rather than dismiss them as a class, based on theoretical concerns. So, for additional enjoyment with your glass of red wine, I recommend reading these reports: 1) Antioxidants and cancer therapy: furthering the debate. Block KI. Integr Cancer Ther. 2004;3(4):342-8. 2) Antioxidants and cancer therapy: a systematic review. Ladas EJ, Jacobson JS, Kennedy DD, Teel K, Fleischauer A, Kelly KM. J Clin Oncol. 2004;1;22(3):517-28. 3) Coenzyme q10 for prevention of anthracycline-induced cardiotoxicity. Conklin KA. Integr Cancer Ther. 2005;4(2):110-30. 4) Effect of radiation therapy on small-cell lung cancer is reduced by ubiquinone intake. Lund EL, Quistorff B, Spang-Thomsen M, Kristjansen PEG. Folia Microbiol 1998;43:505-506. 5) Multiple dietary antioxidants enhance the efficacy of standard and experimental cancer therapies and decrease their toxicity. Prasad KN. Integr Cancer Ther. 2004;3(4):310-22. 6) Rationale for using high-dose multiple dietary antioxidants as an adjunct to radiation therapy and chemotherapy. Prasad KN. J Nutr. 2004;134(11):3182S-3S. --- Kevin A. Hahn, DVM, Ph.D., Dipl. ACVIM (Oncology), is director of Oncology Services at Gulf Coast Veterinary Specialists, Houston (www.gcvs.com/oncology), and is the oncology consultant for YourNetVet (www.yournetvet.com).
