OncologyONCOLOGY Vol 25 No 11
Volume 25
Issue 11

During the 1970s and 80s, several researchers in Canada and in the United States, including those at the National Cancer Institute, studied Essiac. All failed to find any evidence of effectiveness.


Essiac: Burdock (Arctium lappa), rhubarb (Rheum palmatum), sheep sorrel (Rumex acetosella), and slippery elm (Ulmus rubra). Flor-Essence: Essiac, red clover (Trifolium pratense), blessed thistle (Carduus benedictus), kelp (Laminaria digitata), and watercress (Nasturtium officinale).

BACKGROUND: Essiac, a botanical formulation of four herbs, was popularized as a cancer treatment in the 1920s by Rene Caisse, a Canadian nurse (Essiac is Caisse spelled backwards). It is believed that she obtained the formula from a patient who claimed to have learned about it from an Ojibwa healer, and who said that the mixture had cured her breast cancer. Caisse began to use the formula in the form of tea and as an injection to treat cancer patients. However, concerns about the use of Essiac led to an investigation by the Cancer Commission of Ontario in 1938, which failed to find evidence of Essiac’s effectiveness. However, Caisse continued to offer it to patients and modified the original product to further promote its use by adding four more herbs. The new formula, Flor-Essence, was thought to be more potent than Essiac, had improved taste, and could be taken orally by patients, thereby eliminating the need for injection.


Essiac, a blend of four herbs, is a controversial alternative cancer treatment that has been used for over 80 years despite the absence of documented benefit.
Claims for this product are based on patient testimonials and anecdotes.
Patients should avoid use of Essiac, since this may delay conventional care.

For additional information, visit the Memorial Sloan-Kettering Cancer Center Integrative Medicine Service website, "About Herbs," at


During the 1970s and 80s, several researchers in Canada and in the United States, including those at the National Cancer Institute, studied Essiac. All failed to find any evidence of effectiveness.

Despite unsubstantiated claims, Essiac remains a popular anticancer therapy today. Essiac and its variant Flor-essence are manufactured by various companies and marketed worldwide in the form of powders, capsules, teas, and liquid extracts. Promoters claim these products reduce tumor burden, enhance immune response, relieve pain, reduce toxic effects of chemotherapy, and improve survival.

RESEARCH: In vitro studies show that Essiac has antioxidant[1] and cytotoxic properties[2,3]; however, it also stimulated growth of human breast cancer cells.[4] Studies of its antiproliferative effects on prostate cancer cells also yielded conflicting results.[5,6]
Remission of hormone-refractory prostate cancer was reported in one patient,[7] but a retrospective study of breast cancer patients found that Essiac did not improve quality of life or mood.[8]

ADVERSE REACTIONS: A 59-year-old woman reported symptoms of anorexia, nausea, myalgia, fatigue, and generalized abdominal pain following consumption of Essiac over a 6-month period; her symptoms resolved after discontinuing the tea.[9] The manufacturer of Flor-Essence states that users may experience increased bowel movements, frequent urination, swollen glands, skin blemishes, flu-like symptoms, or slight headaches.[10]

HERB-DRUG INTERACTIONS: Decreased clearance of an experimental chemotherapy drug was reported in a patient taking Essiac.[11] This may have been due to inhibition of several cytochrome P450 enzymes by Essiac.[2]

Other Complementary and Alternative Medicine (CAM) Therapies
Commonly Used by Patients With Breast Cancer

The following CAM therapies are among those most often used by patients with breast cancer. Most are initiated to combat the cancer or the effects of its treatment; others are among those patients may have been using before cancer was diagnosed. The potential effects and possible interactions of each with more standard breast cancer therapies are given.

Herbal Supplements

Black cohosh–May have additive effects when used with tamoxifen; it can also increase the toxicity of doxorubicin and docetaxel.

Dong quai–Stimulates proliferation of breast cancer cells and has additive effects with anticoagulants.

Medicinal mushrooms (maitake, reishi, and coriolus)–Because of their immunomodulating effects, these may interact with both immunostimulants and immune-suppressants.

Red clover–Has estrogenic activity and can stimulate growth of breast cancer cells; it also has additive effects with anticoagulants.

Soy–Antagonizes the effects of tamoxifen on estrogen receptor–positive breast cancer.

Whole Medical Systems

Traditional Chinese medicine–Regimens include herbal use, acupuncture, and dietary recommendations; these have potential for herb-drug interactions.

Ayurveda–Treatments consist of detoxification, adherence to strict dietary principles, herbal supplements, and yoga; there is potential for herb-drug interactions.

Supportive Therapies

Massage therapy
Music therapy
Guided Imagery
Relaxation techniques

These are noninvasive therapies and techniques that help control symptoms; adverse effects and interactions are rare.



1. Leonard SS, Keil D, Mehlman T, et al. Essiac tea: Scavenging of reactive oxygen species and effects on DNA damage. J Ethnopharmacol. 2007;103:288-96.

2. Seely D, Kenney DA, Myers SP, et al. In vitro analysis of the herbal compound Essiac. Anticancer Res. 2007;27:3875-82.

3. Taj J, Cheung S, Wong S, Lowe C. In vitro comparison of Essiac and Flor-Essence on human tumor cell lines. Oncol Rep. 2004;11:471-6.

4. Kulp KS, Montgomery JL, Nelson DO, et al. Essiac and Flor-Essence herbal tonics stimulate the in vitro growth of human breast cancer cells. Breast Cancer Res Treat. 2006;98:249-59.

5. Ottenweller J, Putt K, Blumenthal EJ, et al. Inhibition of prostate cancer-cell proliferation by Essiac. J Altern Complement Med. 2004;10:687-91.

6. Eberding A, Madera C, Xie S, et al. Evaluation of the antiproliferative effects of Essiac on in vitro and in vivo models of prostate cancer compared to paclitaxel. Nutr Cancer. 2007;58:188-96.

7. Al-Sukhni W, Grunbaum A, Fleshner N. Remission of hormone-refractory prostate cancer attributed to Essiac. Can J Urol. 2005;12:2841-2.

8. Zick SM, Sen A, Feng Y, et al. Trial of Essiac to ascertain its effect in women with breast cancer (TEA-BC). J Altern Complement Med. 2006;12:971-80.

9. Kessenich CR, Higgs D. Herbal tea components and liver function. Nurse Pract. 2010;35:10-1.

10. Flora Flor
•Essence®. Burnaby, Canada: Flora Manufacturing & Distributing Ltd. Accessed on March 3, 2011. 

11. Geyer C, et al. Dose-schedule optimization of the hexacyclic camptothecin (CPT) analog dx-8951f: a phase I and pharmacokinetic study with escalation of both treatment duration and dose (meeting abstract). Proc Annu Meet Am Soc Clin Oncol. 1999;18.

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