BACKGROUND: Breast cancer is a major cause of morbidity, mortality, and medical expenditures among women in Canada. Essiac (Resperin Canada Limited, Waterloo, Ontario, Canada), a blend of at least four herbs (burdock root [Arctium lappa], Indian rhubarb [Rheum palmatum], sheep sorrel [Rumex acetosella], and the inner bark of slippery elm [Ulmus fulva or U. rubra]), has become one of the more po...