Cancer: Ginseng, Flaxseed Show Promise

At the American Society of Clinical Oncology's annual meeting this weekend, researchers presented dozens of studies of high-tech approaches for fighting cancer—but on Saturday, it was the low-tech tactics that were drawing attention. Three popular complementary and alternative therapies for cancer and cancer-related conditions—flaxseed, ginseng and shark cartilage—came up for review in rigorous trials. The first two showed surprisingly promising results. The third, shark cartilage, failed, but that in and of itself will have major implications, since cartilage is sold widely in health-food stores across the country. Here's the lowdown on all three studies, and what they mean for the future of cancer treatment.

Flaxseed
Nutritionists and alternative-medicine practitioners alike are enamored of flaxseed. High in omega-3 fatty acids, it also has "800 times more lignan than anything else you could stick in your mouth," says Duke University cancer researcher Wendy Demark-Wahnefried. Lignan, a chemical found in the cell walls of plants, binds to testosterone in the body—and in many prostate-cancer patients, testosterone is what fuels tumor growth. Researchers have often suspected that lignan might stop prostate tumor cells from multiplying out of control. Before starting her most recent research, Demark-Wahnefried says, her team "put a man with rising [prostate-specific antigen or PSA] levels on flaxseed, and in three months his PSA had halved and his cancer cells were shrinking. We were pretty jazzed up." A later study also found that mice, genetically programmed to develop prostate cancer, had far less disease when their diets contained flaxseed.

For the study presented at ASCO, the researchers wanted to know what the flaxseed was doing in the body— "if it had an effect on the biology of the tumor and how fast it was dividing," Demark-Wahnefried says. The short answer: it did. About half the 161 prostate-cancer patients in the new study were asked to eat three rounded tablespoons of flaxseed per day for a few weeks. They then underwent surgery to have their tumors removed. On post-surgical examination, "their cancer cells were dividing at a much less rapid clip," says Demark-Wahnefried, perhaps because they had less access to active forms of testosterone.
Scientists don't know if healthy people who eat a lot of flaxseed are at a lower risk for prostate cancer. There certainly aren't a lot of those people, Demark-Wahnefried notes: "People in the Middle Ages made a lot of flaxseed flour and cereals, but these days it's gone out of favor, and we don't eat it that much anymore except sprinkled on yogurt or used as a garnish in bread." But with the new, positive data—and with preliminary work also suggesting that flaxseed can help patients with other hormone-responsive tumors, such as breast cancer—flaxseed may start appearing on a lot more dinner tables soon.

Ginseng
One of the most popular herbs sold around the world, ginseng has a long history in Chinese medicine. Both the American and Asian varieties are considered in traditional Chinese medicine to be "adaptogens," or herbs that help the body react well to physiological insults. "Ginseng wouldn't necessarily work the same way in everybody, according to traditional Chinese philosophy," says Debra Barton, an associate professor of oncology at the Mayo Clinic who presented new data on ginseng at ASCO. "That's a concept that is counter to the way we do research in Western medicine—we want everything to be standardized." Nonetheless, Barton set out to do a randomized, controlled clinical pilot study, the first to look closely at American ginseng's effects on cancer-related fatigue, and its results are striking. The study divided 282 patients into four groups. They were randomly assigned to receive, respectively, 750 milligrams of ginseng per day, 1,000 milligrams, 2,000 milligrams, or a placebo. Those who received the higher doses of ginseng fared better on several measures of energy and well-being, and they also reported much more satisfaction with their overall course of treatment.

There's still a great deal of work to be done on ginseng before doctors can start recommending it to cancer patients in search of an energy boost. "The study still doesn't answer the question of whether ginseng really works," Barton notes. "We need a larger, more definitive trial." If it is in fact working, scientists still have to figure out how. Their best idea so far is that its effects are caused by two specific "ginsenosides," compounds that have been proven to increase endurance in rats. American ginseng contains high levels of one ginsenoside, RB1, while Asian ginseng is rich in the other, RG1. Some hypotheses suggest that ginseng might improve the body's innate responses to stress, but how exactly it might do that is still "anybody's guess," says Barton. It may not be so unclear for long, though. Barton's next study will focus on the relationship between ginseng and stress in cancer patients. In the meantime, patients who really want to take ginseng now instead of waiting until the next study can at least get their hands on the same formulation that Barton's study used: it's available by contacting the administrators of ginsengboard.com.

Shark cartilage
Charles Lu's study of shark cartilage was some of the most disappointing research to come out of the ASCO meeting, but its results are also some of the most important. Long hailed by alternative-medicine enthusiasts as a promising treatment for many types of cancer, shark cartilage has also attracted the attention of mainstream medicine. Lu's trial, the first large one to study the substance's use in cancer treatment, focused on AE-941, a "pharmaceutical-grade" formulation of cartilage developed by the cancer-drug company Aeterna Zentaris. "There was certainly encouraging Phase I and II data for it," says Lu, an oncologist at the University of Texas's M. D. Anderson Cancer Center. "But with any cancer treatment, until you do the clinical trial, you do not know if your laboratory data and early clinical studies will be confirmed. So I guess I'm not shocked."

Sharks have a reputation for having very low rates of cancer, although a study from 2004 revealed that the reputation may not be warranted—the fish certainly do get the disease. In any case, the popular myth wasn't the basis for Lu's study, he says: "It's interesting but irrelevant." What intrigued him more was the fact that shark cartilage contains chemicals that stop the growth of blood vessels—an "anti-angiogenic" effect that mirrors the mechanisms of more conventional tumor-killing drugs. Block the tumor's blood supply, the thinking goes, and you essentially starve it to death.

Alas, any anti-angiogenic effects the shark cartilage may have had in the test tube didn't translate to Lu's 384 human patients. All of the patients had advanced lung cancer, and all were treated with chemotherapy and radiation, but half also drank eight ounces of a shark-cartilage solution each day. Sadly, the second group lived no longer than the first. In fact, they actually did a little worse: They lived for 14.4 months on average after starting the trial, while the placebo group lived an average of 15.6 months. The difference is not statistically significant, so for all practical purposes, the cartilage had no effect, says Lu. As for the previous preliminary studies that showed a positive effect, he adds, "they could have been a statistical fluke." Aeterna Zentaris no longer lists AE-941 as being in development. But Lu says he suspects cancer patients will continue to ask him about shark cartilage anyway, hopeful for any piece of further good news. Before the trial, he says, "I would always say we really don't have any good data. Now I would say there is one large respectable study." And if patients insist on spending their money, he adds, they should spend it on "something that has more promise."

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