Mistletoe is the common name for obligate hemi-parasitic plants in several families in the order Santalales. These plants grow attached to and penetrating within the branches of a tree or shrub by a structure called the haustorium, through which they absorb nutrients from the host plant.
Available clinical evidence does not support claims of anti-cancer effect, quality of life, or other outcomes from the use of mistletoe extract. Research has likewise shown little or no improvement in rigorous trials.
Mistletoe leaves and young twigs are used by herbalists, and it is popular in Europe, especially in Germany, for treating circulatory and respiratory system problems. Use of mistletoe extract in the treatment of cancer originated with Rudolf Steiner, the founder of Anthroposophy. He compared the parasitic nature of the mistletoe plant to that of cancer, and believed that cancer represents a faltering of the body's spiritual defenses. Some anthroposophical mistletoe preparations are diluted homeopathically. Mistletoe extract is sold as Iscador, Helixor, and several other trade names.
Public interest in the United States was spurred in 2001 following actress Suzanne Somers' decision to use Iscador in lieu of chemotherapy following her treatment for breast cancer using surgery and radiotherapy.