Mistletoe

[beach sunrise]

Iscador/Mistletoe
Iscador is a liquid extract from the mistletoe plant (Viscum album) that has been used to treat tumors for more than 60 years (Hajto et al., 1990a). A complex mixture, iscador has two properties that are thought to make it effective against tumors. Iscador is cytostatic and sometimes cytotoxic–that is, it can stop cell growth, sometimes even killing cells. In addition, iscador has immunostimulatory properties, affecting the immune system. Two protein components of the mistletoe extracts appear to be the major active ingredients, viscotoxins and lectins (Jung et al., 1990).

The mistletoe lectins have been studied in more detail than the viscotoxins. In general, lectins are a group of sugar-containing proteins that are able to bind specifically to the branching sugar molecules of complex proteins and lipids on the surface of cells. Certain lectins have both cell-killing and immunostimulatory activity. Their toxic effect occurs because they can stop protein synthesis in cells.

Viscotoxins can kill cells but do not act on the immune system. They act by injuring cell membranes. Considering the toxic properties of both major active ingredients of mistletoe extracts, it is not surprising that mistletoe itself can be poisonous and that proponents of iscador provide cautions about how much to take.

One study examined a lectin from a proprietary mistletoe extract that has been reported to show ability to affect the immune system in rabbits (Hajto et al., 1989). When a tissue culture of certain white blood cells was exposed to this lectin, increased secretion of certain immune system products resulted, including TNF alpha and interleukins 1 and 6, which are cytokines (see the glossary). In turn, there was an increase in the number and activity of certain types of white blood cells. A corroborating increase was seen in cytokine levels in serum of patients after injection of lectin doses (Hajto et al., 1990b).

Both the cell-killing and the immunostimulatory activities of iscador could potentially affect tumor cells. Whether iscador is an appropriate treatment for cancer has been the subject of at least 46 published clinical studies (6 collective reports, 5 small historical studies, 9 large historical studies, 14 retrospective studies, 10 prospective studies, and 2 randomized studies), which were reviewed by Helmut Kiene (Kiene, 1989). None of the studies fit the format of a controlled, randomized, double-blind clinical trial (see app. F). Kiene points out that such studies would be difficult to do because visible local skin irritations appear early in mistletoe treatments; thus both patient and doctor would know about the treatment.

Of 36 studies that Kiene decided were evaluable, he reported that 9 showed positive, statistically significant effects against diverse cancers, including ovarian, cervical, breast, stomach (postoperative), colorectal, and bronchial cancers and liver metastases. Usually the effect was to lengthen the survival time of the patient, commonly measured as median or average survival time; in one study, a significant reduction in the use of painkillers and psychopharmaceuticals was observed (see the glossary). The reviewer noted that the effect of mistletoe therapy tended to appear in situations involving patients with advanced stages of disease rather than patients with less advanced illness.

The antitumor effects observed in these studies with people are supported by studies with animal tumors. Furthermore, except for skin irritations, few uncomfortable side effects are reported by patients. This finding contrasts with the discomforts associated with more traditional anticancer radiation treatments and chemotherapy.

Much of the previous research was conducted in Germany, and the lead organization for a new study is also based there. NCI’s Physicians’ Data Query index identifies this study as a Phase III randomized trial of adjuvant treatment with INF-A (interferon alpha) versus INF-G (interferon gamma) versus mistletoe extract (iscador M) versus no further treatment following curative resection of high-risk stage I/IIB malignant melanoma. A three-volume compendium of research papers on iscador, including translations of some from German, is available (Scharff, 1991).