Mistletoe has been used for centuries for its medicinal properties. Reviewed in [1,2,3,4,5,6] It was reportedly used by the Druids and the ancient Greeks, and it appears in legend and folklore as a panacea. It has been used in various forms to treat cancer, epilepsy, infertility, menopausal symptoms, nervous tension, asthma, hypertension, headache, and dermatitis. Modern interest in mistletoe as an anticancer treatment began in the 1920s. Reports of more than 30 clinical studies of mistletoe as a treatment for people with cancer have been published since the early 1960s.[7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36] Reviewed in [3,37,38] Most of the results of these studies were published exclusively in German. (Refer to the Human/Clinical Studies section of this summary for more information.)
As indicated previously (refer to the General Information section of this summary for more information), proposed mechanisms of action for mistletoe that are relevant to cancer include stimulation of the immune system [7,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68] Reviewed in [1,2,3,8,9,10,11,37,38,69,70,71,72] and a direct toxic effect on tumor cells.[73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89] Reviewed in [1,69,71,90]. Another reported activity that may be relevant to optimum functioning of the immune system in individuals with cancer is stabilization of the DNA in white blood cells, including white blood cells that have been exposed to DNA-damaging chemotherapy drugs.[91,92,93,94] Reviewed in 
Scientists study risk factors and protective factors to find ways to prevent new cancers from starting. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.
Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Risk factors that a...