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Mar 24, 2001 (United Press International via COMTEX) -- Cancer patients who try supplements and vitamins to combat their disease may regain some sorely needed sense of control, but medical experts caution that untested remedies can possibly do more harm than good.
In recent years, researchers the effects herbs and vitamins may have on cancer progression is receiving more attention from researchers who are curious to know whether these supplements can not only impact disease development, but also influence the effectiveness of conventional treatments, such as radiation and chemotherapy.
However, scientists are still in the embryonic stage of understanding dietary supplements, Dr. Jeff White, director of the National Cancer Institute's office of cancer, complementary and alternative medicine, told United Press International.
Little concrete data are yet on record, and until researchers know more about certain supplements, cancer care specialists should discourage patients from using them, said Dr. Wendy Weiger at a recent medical meeting on alternative medicine.
Weiger, a research fellow in medicine at Harvard Medical School, Boston, said one area of concern is antioxidant vitamins such as C and beta-carotene. Study findings have already suggested they may help prevent cancer, but evidence is surfacing now as well about their role in patients diagnosed with cancer.
"Antioxidants have the potential to increase or decrease the efficacy of conventional radiation and chemotherapy," Weiger said.
White echoed that sentiment: "Some chemotherapy drugs seem to kill cancer cells by inducing oxidation in the cell," he said, "and antioxidants, theoretically, might interfere with that reaction."
At an American Cancer Society meeting last year, doctors from Memorial Sloan-Kettering Cancer Center in New York said high doses of vitamin C supplements might actually protect tumors from radiation. That doesn't mean cancer patients can't enjoy an orange or a grapefruit, or even take vitamin C as part of a multivitamin, they said, but large amounts of concentrated vitamin C may be a problem.
Weiger also pointed out some supplements' active components remain a mystery, posing a threat to cancer patients. She pointed to a Chinese remedy as an example. Called PC-SPES, the remedy contains eight different herbs, is available in health food stores, and has often been used by prostate cancer patients.
In a study published in the September 17, 1998 issue of The New England Journal of Medicine, researchers found men who took PC-SPES experienced drops in prostate specific antigen, a protein associated with prostate cancer, and testosterone. At the same time, these cancer patients also felt breast tenderness and a deteriorating sex drive.
"PC-SPES," the investigators wrote, "has potent estrogenic activity. The use of this unregulated mixture of herbs may confound the results of standard...therapies."
However, White said it's too early to rule out such herbal remedies.
"Estrogen compounds may offer benefits to prostate cancer patients," he said. "I think it's still an open question."
Another questionable herb is Essiac, said Weiger. Reports from Canada have found this product to be popular among breast cancer patients, but no studies have yet demonstrated either its potential benefits or risks. Laboratory tests do indicate Essiac contains estrogen-like compounds and may produce laxative effects.
Experts say breast cancer patients should be extremely aware of any supplement containing estrogenic properties, including soy, a very popular supplement among women.
"If you have cancer that's feeding on estrogen (like breast cancer), that could make it worse for you," said Carol Gotay, a researcher and professor at the University of Hawaii Cancer Research Center in Honolulu.
Gotay added supplements carrying estrogen could be particularly harmful to breast cancer patients taking Tamoxifen, a drug that destroys breast cancer cells by disabling estrogen, a point Weiger highlighted as well. Diets high in estrogen, such as the Macrobiotic diet, an Asian-influenced, heavily vegetarian diet, might also be a risk to breast cancer patients, Weiger said. "We hope future research will help us sort out the wheat from the chaff," she said.
But White cautioned that even with the need for more research, oncologists who immediately dismiss complementary therapies may alienate their patients -- who might then take the supplements anyway without disclosing it to their doctors.
"To automatically reject supplements without a rationale behind it is a turnoff to patients," he said. Studies down the road may indicate that "certain types of supplements used in certain ways may be beneficial."
By KATRINA WOZNICKI, UPI Science News
Copyright 2001 by United Press International.
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