Anti-cancer effects of fenbendazole, albendazole, and mebendazole have been known against cancer cell lines in vitro for a long time.1 Microtubule destabilization is suggested as a mechanism of action.2 Based on these findings, clinical trials have been done for cancer patients with albendazole or mebendazole.3 One Swedish clinical trial was initiated on August 11, 2018 and terminated on January 22, 2020 due to lack of effect after enrollment of 11 cancer patients.4 There is no definite evidence of anti-cancer effects in human patients so far. Clinical trial with fenbendazole is impossible, because it is not permitted for human use due to toxicities.

Food and Drug Administration (FDA) and European Medicines Agency (EMA) prohibit fenbendazole for human use. Recommended dosage for animal is 5 mg/kg, which is more than 100 fold acceptable daily intake for human safety (40 micrograms per kilogram body weight). The decision was based on toxicity and teratogenicity studies conducted in Hoechst Research Laboratories (NADA 128-620).5 Actual toxicities, such as acute hepatitis, following self-administration of fenbendazole are reported.

Even though the Korean Ministry of Food and Drug Safety warned that this claim was unfounded and that side effects of such drugs could damage patients, the outbreak of the anthelmintics is still ongoing. A conspiracy theory argues that pharmaceutical companies are interfering with clinical trials of anthelmintics in cancer patients. However, it is not true because several clinical trials have been done with support from companies (clinicaltrials.com).

Claiming to cure terminal cancer patients with untested new drugs or food supplements have repeatedly appeared under media spotlight and disappeared. The desperation of terminal cancer patients and their families is fully understood emotionally, clinging to claims that there is even a slight possibility of catching straws.

As a Greek philosopher, Jamblichus, wrote 2000 years ago: “Medicine is the daughter of dreams.” This message remarkably still resonates today. When faced with a bleak or uncertain reality, we tend to pursue "dreams” or hope. However, rather than questioning whether our dreams are valid, we naively cling to the presence of dreams. Such dreams inevitably become stronger than rational thought.

In the internet environment where anyone can easily access various untested medical data, information is delivered without filtration and the propagation speed is surprisingly fast. Claims are not always facts. Unverified medical information is causing confusion or unnecessary pain rather than helping patients and their families.

In order to minimize such unnecessary confusion, objective verification through evidence-based medicine is required. Additional efforts of experts are needed to disseminate validated medical information to the public (especially patients).