The websites and other resources your patients find on the Internet may not only be providing false or unsubstantiated information regarding the cancer-fighting benefits of untested herbal supplements, they may also be downplaying or ignoring clinical evidence that these supplements may promote tumor growth or impair the effectiveness of established cancer treatments.
The popularity of a variety of so-called “complementary” or “alternative” medical strategies employed by the public has been well documented
. It is also increasingly appreciated that cancer patients pursue a wide variety of treatment approaches outside the medical mainstream for dealing with symptoms of cancer, side effects of treatment, and potentially intense emotions like anxiety and fear that follow a cancer diagnosis. Both the hypothesized benefits and potential risks associated with a wide spectrum of such strategies have been extensively discussed in the medical and lay literature
One specific form of alternative medicine that should be of particular concern to oncologists and other cancer health professionals is the increasing prevalence of individuals with cancer who elect to self-administer or receive from a practitioner a variety of herbs or other untested “medications” (eg, high-dose vitamin C). These approaches may be utilized to directly treat the cancer (eg, through “augmentation” of natural immunity) or prevent or ameliorate the toxic effects of standard anti-neoplastic drugs.
Although the existence of alternative cancer treatments for which there are unsubstantiated (and subsequently disproved) claims of direct benefits is certainly not a new phenomena (eg, laetrile), what is of increasing concern is objective evidence that a number of these essentially unregulated supplements and pharmaceuticals may actually cause harm. In fact, there is a growing body of pre-clinical and clinical data that indicates that when some of these unproven but biologically active agents are taken by an individual (with or without cancer), serious and completely unanticipated consequences may result (see sidebar).
Several disquieting evaluations of such products reported in the recently published medical literature emphasize this point. The observation of two men who developed aggressive prostate cancer shortly after taking the same herbal dietary supplement designed to “solve health and aging issues” led to an examination of the effect of the product on cancer cell growth. Tested against established prostate cancer cell lines, the investigators
found this preparation to be “a more potent dose-dependent stimulator of cancer cell growth than testosterone both in androgen receptor-negative and receptor-positive cell lines.”
In another report
, a dietary supplement “advertised to ameliorate female sexual dysfunction” was demonstrated in an in vivo
model to result in the growth of estrogen-dependent breast cancers. Finally, two laboratory-based studies have revealed that the supplement genistein, employed to ameliorate post-menopausal symptoms, may impair the anti-neoplastic activity of both tamoxifen
It must be emphasized that these are only a few examples of tested products. How many other alternative medications are being taken by an unsuspecting public that may result in serious consequences related to cancer progression or interfere with the effectiveness of established anti-neoplastic therapy?High-concentrations of Vitamin C
Whereas the lack of evidence for the benefit of alternative medications is of legitimate concern, perhaps the greatest potential danger of such approaches is the risk that a particular product may actually directly prevent an established anti-neoplastic agent from killing a viable tumor.
Recently reported experimental data
regarding the ability of vitamin C, in a dose-dependent manner, to protect cancer cells from the cytotoxic effects associated with a variety of important and widely utilized anti-cancer drugs (doxorubicin, cisplatin, vincristine, methotrexate, imatinib) have rather profoundly changed this discussion from an abstract concern to a potentially serious health hazard. The fact that this negative effect of vitamin C was so broad-based suggests that the protective influence relates to a fundamental mechanism of tumor cell killing and may be operative when essentially any anti-neoplastic agent is administered to treat a human cancer.