Taking a peek at Mistletoe Therapy and how it compares with other emerging cancer treatments
As we approach Christmas, many of us adorn our houses with swathes of holly and ivy along with a sprig of mistletoe. Mistletoe has a history in traditional folklore connected to fertility and healing. Today, it is also gaining recognition in integrative veterinary medicine as a supportive therapy for animals facing cancer. More commonly than being asked about mistletoe therapy, we are approached about drugs like the common de-wormer Fenbendazole. Owners query whether it has potential as a cancer treatment for both humans and their pets. Understandably, many animal owners feel overwhelmed by the weight of decision-making for a pet with cancer. Importantly, they need answers to questions surrounding safety and effectiveness of treatments.
At A.P. Vet we don’t use conventional medicines although, as fully trained vets, we know all about them. Instead, we leave the prescribing of veterinary medicines to the referring first line vet. Even over-the-counter drugs can be problematic and we encourage owners to discuss them with the referring first line vet.
The Benzimadole Family of Drugs
Fenbendazole
Our vets support the use of anti-parasitic drugs when parasites have been identified in a pet. We consider, however, that routine worming or defleaing is unnecessary unless a parasite is actually present or there is a high-risk situation. The use of anti-parasitic Fenbendazole for animal cancer care is presently unapproved and safe dosage levels are unavailable. We find it problematic that it is used indiscriminately and long term in some animal cancer cases.
There is very little data on the safety of long-term use. Due to certain clinical conditions, rabbits are commonly treated, and sometimes longer term, with Fenbendazole. There are rather concerning reports about worrying long-term effects, sometime fatal (Graham et al, 2014). The study includes results from 13 rabbits of which one survived with supportive therapy and 12 died. The toxic effects found were anaemia, leukopenia, and thrombocytopenia. In that context, checking bloods, especially haematology, seems a good idea when Fenbendazole is used on a long-term basis.
Albendazole
Like Fenbendazole, Albendazole is a drug classed as benzimidazole. In clinical trials, Albendazole showed some efficacy in the treatment of refractory and metastatic tumours, with actions that include tumour stabilisation, regression, and reduction in tumour markers. Neutropenia, however, was reported as a side effect. (DS Son et al 2020). Myelosuppression, fatigue and mild gastrointestinal upset are also known side effects of Albendazole.
Does Fenbendazole Work?
Fenbendazole has not been a focus of clinical trials to date, mostly due to a lack of safety studies, although the drug receives considerable coverage on the web because it is readily available for cancer patients seeking alternative self-driven therapies (Yamaguchi et al, 2021).
Fenbendazole binds tubulin, which is how it has the antiparasitic effect. That mechanism is utilised in antimitotic cancer drugs. They have only been proven in rabbits (Graham et al 2014) and human patients (Yamaguchi et al 2021). So far, to our knowledge, no studies were done in dogs. At A.P. Vet Ltd. we feel strongly that, if trying to utilise such a potent pharmacologic effect, careful monitoring of side effects is warranted. It is of real concern that desperate owners with poorly pets choose to use drugs like Fenbendazole without seeking advice regarding suitability or possible interactions with other medications.
Mistletoe Therapy
Our vet, Iris Ege, has treated many animals with Mistletoe extract (Iscador) with both oral and injectable formulations depending on case history and species. Cats, for instance, generally tolerate oral Iscador better than an injectable form.
Summary
The use of Fenbendazole in oncology is still speculative at this stage as insufficient research exists. Mistletoe-extract, Iscador, offers a longer-established supportive choice in veterinary cancer care. Mistletoe therapy has been used in cancer cases in cats, horses and dogs. Regardless of owner preference, the first line vet should always be consulted before either of the treatments is considered. If a treatment route is followed, it is critical to keep all professionals involved in the animal’s care up to date. This should minimise risks of any negative interactions between drugs or other therapies.
Like so many of our clients, we hope for improved animal cancer care options, supported by robust clinical research. We cannot, however, over-emphasise the importance of thorough diagnostics and getting sound veterinary guidance throughout the cancer journey.
Please contact us for further information.
References
Graham, Jennifer & Garner, Michael & Reavill, Drury. Benzimidazole Toxicosis in Rabbits: 13 Cases (2003-2011). Journal of Exotic Pet Medicine, 2014, Volume 23, Issue 2.
Son DS, Lee ES, Adunyah SE. The Antitumour Potentials of Benzimidazole Anthelmintics as Repurposing Drugs. Immune Netw. 2020 Aug; 20(4). https://doi.org/10.4110/in.2020.20.e29
Yamaguchi T, Shimizu J, Oya Y, Horio Y, Hida T. Drug-Induced Liver Injury in a Patient with Nonsmall Cell Lung Cancer after the Self-Administration of Fenbendazole Based on Social Media Information. Case Rep Oncol. 2021 Jun 17; 14(2):886-891.
