Botanicals Used in Complementary Cancer Treatment: A Review of Safety and Efficacy

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  • Botanicals
  • Cancer
  • Chemoprevention
  • Date: February 15, 2005 HC# 010351-274

    Re: Botanicals Used in Complementary Cancer Treatment: A Review of Safety and Efficacy

    Boon H, Wong J. Botanical medicine and cancer: a review of the safety and efficacy. Expert Opin Pharmacother. 2004;5(12):2485-2501.

    More than 50% of cancer patients utilize complementary and alternative medicine (CAM) therapies; however, information on the efficacy and safety of the most frequently utilized herbal medicines for cancer has not been condensed into one readily available source. The current study sought to review the evidence for the safety and efficacy of "commonly used herbal products" for the treatment of cancer or to mitigate the adverse effects of conventional treatment.

    The researchers first identified the most commonly used herbs by reviewing previously published surveys in which CAM use by cancer patients was reported. They then looked for data on each herb by searching on Medline, the U.S. National Institutes for Health's (NIH) database, for articles published between 1966 and July 2004, and on Embase, for articles between 1980 and July 2004. The herbs or preparations reviewed were Asian ginseng (Panax ginseng); essiac, a mixture of four or more herbs; evening primrose oil (Oenothera biennis); garlic (Allium sativum); ginger (Zingiber officinale); green tea (Camellia sinensis); mistletoe (Viscum album); reishi (Ganoderma lucidum); shiitake (Letinus edodes); soy (Glycine max); tomatoes (lyocpene); and turmeric (Curcuma longa).

    Some studies concluded that the herbs helped while other concluded that they did not help or were harmful. For example, fresh ginseng extract, red ginseng, and white ginseng extract or powder significantly reduced the incidence of cancer in several studies reviewed. Ginseng provided a 45-80% reduction in colorectal cancers, cancers of the GI tract, lungs, ovaries, and pancreas. Green tea, when > 10 cups per day are consumed, appeared to decrease the risk of breast, GI, lung, ovarian, prostate, and urinary system cancers by 9-29%. Other reports seemed to contradict the risk for these cancers, however, with four studies concluding that green tea increases the risk of bladder, lung and stomach cancers. Soy decreased the incidence of breast, lung, stomach, endometrium, prostate, and thyroid cancer by 46-85% in 17 studies. However, 10 other studies determined that soy intake did not affect the risk for breast, GI lung, and prostate cancers, while increasing the risk for bladder, esophageal, and prostate cancers.

    Two randomized, double-blind trials evaluated ginger in treating nausea and vomiting from chemotherapy. In one study, ginger was given with the anti-nausea drug, compazine, and in the second study, ginger was given alone and compared with two standard anti-nausea medications. Only in the second study was ginger determined to be effective at treating nausea in these patients. The research on mistletoe is equally contradictory. Four trials showed an improvement in cancer patient outcomes while four other studies concluded no significant benefits. Two mistletoe studies did show a reduction in adverse effects from conventional treatment.

    The authors conclude that Asian ginseng, garlic, green tea, tomatoes, and soy all may help prevent cancer. Data on the usefulness of essiac, evening primrose oil, mistletoe, reishi, shiitake, and turmeric to treat cancer needs additional research. Also, ginger may be effective at treating nausea and vomiting from conventional cancer therapies.

    While this study provides a good list of clinical trials and reports some of the data from those trials, it is difficult to draw many clinically relevant conclusions from it. The authors pooled data from disparate study populations (e.g., people with different cancers, difference stages of cancer, different ages, and possibly on different conventional, treatment regimens).

    Data from various studies used different protocols (e.g., different concentrations of herbal extracts and different dosages of herbs). When data is pooled, possible benefits or adverse effects based on different dosages of the herb, different cancer types or stages, or different clinical trial protocols can be missed. However, the researchers do show that adverse effects were rarely associated with the herbs taken. Few randomized, double-blind, placebo-controlled trials have been conducted on these herbs and additional research is needed.

    —John Neustadt, ND4

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