Shark cartilage tanks; flaxseed and ginseng may be useful

Yesterday morning's press release from the American Society for Clinical Oncology (ASCO) meeting included discussion of three abstracts on complementary therapies being tested in cancer and cancer-related indications. The highlights on the major news services are that 1) a shark cartilage extract failed to provide survival benefit in patients with non-small cell lung cancer, 2) an American ginseng extract reduced cancer-related fatigue, and 3) flaxseed slows prostate cancer growth.

Just a few comments, mostly on the positive results, that didn't make it into mainstream media reports:

The ginseng study was conducted at Mayo Clinic and gave a variety of 282 cancer patients a placebo or one of three dose levels (750, 1000, and 2000 mg, split between two doses daily) of an American ginseng extract for a total of 8 weeks. (Ginseng contains steroid-like compounds known as ginsenosides that are poorly-described as "adaptogens," or substances that amorphously help the body respond to stress.) Note that the extract can't be compared to anything on the market since it was made for the study from a single source of Wisconsin ginseng. In fact, the press release states that, "The authors also cautioned against store-bought ginseng supplements, citing the lack of regulation and inconsistent quality and safety." Patients had a variety of cancers and those undergoing or having completed radiation or chemotherapy were evenly distributed across the treatment groups. The primary endpoints were self-reported standardized fatigue and vitality indexes and a general overall sense of improved fatigue. In the placebo and 750 mg groups, 10% of patients reported "moderate to very much better fatigue levels" as compared with 25% with the 1000 mg dose and 27% with the 2000 mg dose. So, the improvements were modest and doubling the lowest active dose provided no greater increment of fatigue relief.

The flaxseed study was a multi-center investigation conducted out of Duke University with 161 prostate cancer patients about to undergo prostatectomy surgery in no less than three weeks, with a mean study length of 30 days. The investigators tested flaxseed (30 grams per day) alone or together with dietary restriction of fat (to less than 20 percent calories from fat). (Flaxseed contains omega-3 fatty acids known to slow cancer cell proliferation in culture and lignans that bind steroid hormones like testosterone that promote prostate cancer growth.) After surgery, prostate tumors were stained with an antibody that detects actively dividing cells (MIB-1; Ki-67). The ratio of dividing to non-dividing cells were 2.38 for the control group, 1.71 for the flaxseed group, 2.93 for the low-fat group, and 1.58 for the combined flaxseed/low-fat diet group. So, treatments including flaxseed reduced the fraction of actively growing cells by 30 to 40 percent. The source of the flaxseed was not noted but it did not appear to be any special extract. Further studies for longer periods might provide useful information for prostate cancer patients who are in the "watchful waiting" phase.

The shark cartilage study was a multi-center study (384 patients at 53 sites) conducted out of the University of Texas M.D. Anderson Cancer Center. A proprietary, orally-administered shark cartilage extract (AE-941; AEterna Zentaris) was added to standard chemotherapy and radiation therapy in patients with advanced non-small cell lung cancer termed stage III, a stage which is no longer amenable to surgery. Overall mean survival was 15.6 months in the standard therapy group as compared to 14.4 months when shark cartilage was added, but the difference was not statistically significant. There have been many questions as to whether antiangiogenic substances in shark cartilage remain active after oral administration, but the compounds were not measured in these patients. While this study was negative for this shark cartilage extract, one must also realize that stage III non-small cell lung cancer is a difficult setting in which to have any impact.

(For even more details, see the full press release PDF with abstracts and commentary.)