Am Fam Physician. 2003;67(9):1991-1996
Many patients seek advice from physicians about the use of complementary and alternative medical (CAM) therapies for cancer. CAM therapies are those not usually provided by hospital-based oncology practices, although some are being used more commonly and may eventually fail to meet current definitions. Weiger and associates performed a literature search reviewing dietary changes (fat reduction and radical dietary regimens), the use of antioxidant vitamins, soy, herbs, and other natural products, acupuncture, massage, exercise, and psychologic and mind-body interventions.
Priority was given to the results of randomized controlled trials, although uncontrolled and observational studies were considered when no randomized controlled trials had been completed. Individual therapies were placed along a continuum ranging from “recommend” to “discourage,” which allowed physicians to use existing data to provide evidence-based advice to patients.
The review studies of dietary fat reduction were inadequate to recommend this therapy in women with breast cancer; it is reasonable to accept this method in patients who are well nourished and who elect to try this approach. Although observational studies suggest that reduction of saturated or animal fats slows the progression of prostate cancer, the absence of a randomized trial makes it reasonable for physicians to accept this diet modification in well-nourished men with prostate cancer. Limited data suggest that macrobiotic diets may alter drug metabolism. Highly restrictive diets should be avoided in malnourished patients. The high content of phytoestrogens in some macrobiotic diets may negatively impact on breast cancer (especially estrogen receptor–positive tumors) or endometrial cancer. In well-nourished patients who do not have breast or endometrial cancer, a macrobiotic diet can be accepted by the physician as an adjunct of conventional treatment, but patients must be closely observed for malnutrition or altered metabolism of conventional medications.
The antioxidant vitamins A, C, and E may cause more harm than benefit because of the risks of cancer progression and hypervitaminosis A, anticoagulation effects, and diminished platelet function, respectively. High doses of these vitamins should be discouraged.
Soy supplements should be discouraged in women who have breast cancer because of the phytoestrogen content, and accepted for use by men with prostate cancer who elect to try them. However, soy supplements contain isoflavonoids that may inhibit platelet aggregation.
Numerous herbal products and other biologic agents are frequently used by persons with cancer. PC-SPES, an oral supplement composed of extracts of eight herbs, has been shown to decrease cell growth in in vitro studies of various cancer cell lines and has demonstrated positive effects in five open-label trials. Adverse effects may come from its estrogenic properties. Samples of PC-SPES also have been noted to have intersample variations and to be contaminated with conventional medications including diethylstilbestrol, warfarin, and indomethacin. At present, PC-SPES is currently unavailable because of a hazard warning issued in 2002 by the U.S. Food and Drug Administration (FDA).
Shark cartilage contains proteins that inhibit angiogenesis, but efficacy study results are unclear. Oral shark cartilage has few adverse effects, although gastrointestinal side effects and allergic reactions have been reported. It is reasonable to accept the use of shark cartilage by patients, but its use should be discouraged in patients with hypercalcemia because of the high calcium content in current preparations.
Acupuncture controls chemotherapy-related nausea and vomiting, and can palliate chronic pain. Adverse events are few. It is appropriate to accept the use of acupuncture in conjunction with standard antiemetics to control chemotherapy-related nausea and vomiting among cancer patients.
Massage has not demonstrated any positive effect on cancer progression or pain relief. Dangers of massage include tissue injury, bleeding, embolization of a thrombus, and displacement of stents. Massage to relieve anxiety or ameliorate pain or as an adjunct to treatment of lymphedema is acceptable.
Exercise regimens have not yet become standard adjuncts to cancer therapy and need further study.
Psychologic and mind-body therapies such as individual and group therapy, relaxation, imagery, hypnosis, and meditation can relieve distress and pain as well as some of the physical symptoms of disease and side effects of conventional therapy. Although impact on survival is uncertain, acceptance of these types of therapies is reasonable.
The authors conclude with discussion recommendations for physicians talking to patients about CAM therapies. These include (1) discouraging a therapy that delays conventional treatment, is offered by an unlicensed professional, or involves injections of a non-FDA approved substance; (2) informing patients that natural does not mean safe and that contents of supplements may not be what is on the label; and (3) reviewing specific contraindications to CAM therapy when they are present. Open communication and close follow-up will allow the safest use of CAM therapies in persons with cancer.